diff --git a/README.md b/README.md
index a13a60b..3db2770 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# Awesome Math [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38d29fed78fa85652e3a63e154dd8e8829/media/badge.svg)](https://github.com/sindresorhus/awesome)
+# Awesome Math [![Awesome](https://cdn.jsdelivr.net/gh/sindresorhus/awesome@d7305f38d29fed78fa85652e3a63e154dd8e8829/media/badge.svg)](https://github.com/sindresorhus/awesome)
 
 A curated list of awesome mathematics resources.
 
@@ -79,7 +79,7 @@ All resources are freely available except those with a 💲 icon.
 
 * [Khan Academy](https://www.khanacademy.org/math)
 * [Coursera](https://www.coursera.org/courses?query=mathematics&languages=en)
-* [MIT OpenCourseWare](http://ocw.mit.edu/courses/mathematics/)
+* [MIT OpenCourseWare](https://ocw.mit.edu/courses/mathematics/)
 * [edX](https://www.edx.org/course/subject/math)
 * [Brilliant](https://brilliant.org/courses/#math-foundational)
 * [WooTube](https://misterwootube.com/)
@@ -92,7 +92,7 @@ All resources are freely available except those with a 💲 icon.
 
 ## Learn to Learn
 
-* [Understanding Mathematics](https://github.com/nelson-brochado/understanding-math)
+* [Understanding Mathematics](https://github.com/nbro/understanding-math)
 
 ## Youtube Series
 
@@ -124,12 +124,11 @@ All resources are freely available except those with a 💲 icon.
 * [Wolfram Alpha](http://www.wolframalpha.com/)
 * [Maxima](https://maxima.sourceforge.io/)
 * [Sympy](https://www.sympy.org/)
-* [Sagemath](http://www.sagemath.org/)
+* [Sagemath](https://www.sagemath.org/)
 * [MathFlow](https://github.com/Nonanti/MathFlow) - C# math expression library with symbolic computation (differentiation, simplification, equation solving)
-* [Unit Converter](https://unitconverters.net)
+* [Unit Converter](https://www.unitconverters.net/)
 * [GeoGebra](https://www.geogebra.org/?lang=en)
 * [Macaulay2](http://www2.macaulay2.com/Macaulay2/)
-* [Singular](https://www.singular.uni-kl.de/)
 * [GNU Octave](https://www.gnu.org/software/octave/)
 * [Magma](http://magma.maths.usyd.edu.au/magma/)
 * [Maple](https://www.maplesoft.com/products/Maple/)
@@ -149,13 +148,13 @@ All resources are freely available except those with a 💲 icon.
 
 ## Questions and Answers
 
-* [Mathematics Stack Exchange](http://math.stackexchange.com/)
-* [MathOverflow](http://mathoverflow.net/) - for professional mathematicians
+* [Mathematics Stack Exchange](https://math.stackexchange.com/)
+* [MathOverflow](https://mathoverflow.net/) - for professional mathematicians
 
 ## Encyclopedia
 
-* [Encyclopedia of Mathematics](https://www.encyclopediaofmath.org)
-* [Planetmath](http://planetmath.org/)
+* [Encyclopedia of Mathematics](https://encyclopediaofmath.org/wiki/Main_Page)
+* [Planetmath](https://planetmath.org/)
 * [ProofWiki](https://proofwiki.org/wiki/Main_Page)
 * [Wolfram Mathworld](http://mathworld.wolfram.com/)
 * [The On-Line Encyclopedia of Integer Sequences](https://oeis.org) - Great compendium of many different integer sequences. Founded 1964 by N. J. A. Sloane.
@@ -165,13 +164,12 @@ All resources are freely available except those with a 💲 icon.
 ## Books
 
 * [Calculus: Basic Concepts for High Schools](https://archive.org/details/TarasovCalculus) - L.V. Tarasov
-* [Basics of Algebra, Topology, and Differential Calculus](http://www.cis.upenn.edu/~jean/math-basics.pdf) - Jean Gallier (University of Pennsylvania)
-* [Multivariable Calculus](http://people.math.gatech.edu/%7Ecain/notes/calculus.html) - G. Cain, J. Herod (Georgia Tech)
+* [Basics of Algebra, Topology, and Differential Calculus](https://www.cis.upenn.edu/~jean/math-deep.pdf) - Jean Gallier (University of Pennsylvania)
+* [Multivariable Calculus](https://people.math.gatech.edu/~cain/notes/calculus.html) - G. Cain, J. Herod (Georgia Tech)
 * [Wikibooks](https://en.wikibooks.org/wiki/Wikibooks:Mathematics_bookshelf)
 * [Online Mathematics Textbooks](https://people.math.gatech.edu/~cain/textbooks/onlinebooks.html)
 * [Beginning and Intermediate Algebra](http://www.wallace.ccfaculty.org/book/Beginning_and_Intermediate_Algebra.pdf)
 * [Free Mathematics Books](https://github.com/EbookFoundation/free-programming-books/blob/master/books/free-programming-books-subjects.md#mathematics)
-* [Trigonometry](http://www.mecmath.net/trig/trigbook.pdf)
 * [Math for Frontend Web Dev](https://www.manning.com/books/math-for-frontend-web-dev)
 * [Grokking Statistics](https://www.manning.com/books/grokking-statistics)
 
@@ -202,7 +200,7 @@ All resources are freely available except those with a 💲 icon.
 * [Areas of mathematics on Wikipedia](https://en.wikipedia.org/wiki/Areas_of_mathematics)
 * [Paul's Online Math Notes](http://tutorial.math.lamar.edu/) - Paul Dawkins (Lamar University)
 * [List of electronic textbooks](http://faculty.atu.edu/mfinan/nnotes.html) - Marcel B. Finan (Arkansas Tech University)
-* [Topology Atlas](http://at.yorku.ca/topology/)
+* [Topology Atlas](http://at.yorku.ca/index.html)
 * [Recreations in Math](http://djm.cc/library/Recreations_in_Mathematics_Licks_edited.pdf) - H. E. Licks (1917)
 * [Magic Squares and Cubes](http://djm.cc/library/Magic_Squares_Cubes_Andrews_edited.pdf) - W. S. Andrews (1917)
 * [Convex Optimization](https://web.stanford.edu/~boyd/cvxbook/) - Stephen Boyd and Lieven Vandenberghe
@@ -226,11 +224,11 @@ All resources are freely available except those with a 💲 icon.
 * 📝 [Sets, Relations, Functions](http://www.cosc.brocku.ca/~duentsch/papers/methprimer1.html) - Ivo Düntsch, Günther Gediga
 * 📝 [An Introduction to Set Theory](http://www.math.toronto.edu/weiss/set_theory.pdf) - William A. R. Weiss
 * 📝 [Set Theory and Foundations of Mathematics](http://www.settheory.net/) - Sylvain Poirier
-* 📝 [Set Theory on the Stanford Encyclopedia of Philosophy](http://plato.stanford.edu/entries/set-theory/)
+* 📝 [Set Theory on the Stanford Encyclopedia of Philosophy](https://plato.stanford.edu/entries/set-theory/)
 
 ### Logic
 
-* 📝 [Introduction to Logic](https://pdfs.semanticscholar.org/6967/f52773d9c2ccfc94658657a5761e0f00e95a.pdf) - Michael Genesereth, Eric Kao (Stanford University)
+* 📝 [Introduction to Logic](https://www.semanticscholar.org/paper/Introduction-to-Logic%2C-Second-Edition-Genesereth-Kao/6967f52773d9c2ccfc94658657a5761e0f00e95a?p2df) - Michael Genesereth, Eric Kao (Stanford University)
 * 📝 [An Introduction to Formal Logic](https://www.fecundity.com/codex/forallx.pdf) - P.D. Magnus (University at Albany)
 * 📝 [A Problem Course in Mathematical Logic](http://euclid.trentu.ca/math/sb/pcml/pcml-16.pdf) - Stefan Bilaniuk (Trent University)
 * 📝 [Computability - An introduction to recursive function theory](http://poincare.matf.bg.ac.rs/~zarkom/Book_Math__Cutland_Computability.pdf) - Nigel Cutland (University of Hull)
@@ -240,15 +238,13 @@ All resources are freely available except those with a 💲 icon.
 * 📝 [Formal Logic](http://maude.sip.ucm.es/~miguelpt/papers/flogic.pdf) - Miguel Palomino
 * 📝 [Predictive Arithmetic](https://web.math.princeton.edu/~nelson/books/pa.pdf) - Edward Nelson
 * 📝 [Proofs and Concepts: the fundamentals of abstract mathematics](http://people.uleth.ca/~dave.morris/books/proofs+concepts.html) - Joy Morris, Dave Morris
-* 📝 [Mathematical Reasoning: Writing and Proof](https://www.tedsundstrom.com/mathreasoning) - Ted Sundstrom
 * 📝 [Logic and Proof](http://leanprover.github.io/logic_and_proof/) -  Jeremy Avigad, Robert Y. Lewis, and Floris van Doorn
-* 📝 [QED - an interactive textbook](https://teorth.github.io/QED) - Terence Tao
+* 📝 [QED - an interactive textbook](https://teorth.github.io/QED/) - Terence Tao
 * 📝 [Open Logic Textbook](http://builds.openlogicproject.org/) - collaborative effort, main contributors listed [here](https://openlogicproject.org/people/)
 
 ### Category Theory
 
 * 📝 [Introduction to Category Theory and Categorical Logic](http://www.mathematik.tu-darmstadt.de/~streicher/CTCL.pdf) - Thomas Streicher
-* 📝 [An Introduction to Category Theory](http://www.cs.man.ac.uk/~hsimmons/zCATS.pdf) - Harold Simmons
 * 📝 [Category Theory](http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.211.4754&rep=rep1&type=pdf) - Steve Awodey (Carnegie Mellon University)
 * 📝 [Category Theory](http://www.mathematik.uni-muenchen.de/~pareigis/Vorlesungen/04SS/Cats1.pdf) - B. Pareigis
 * 📝 [Category Theory for Computing Science](https://web.archive.org/web/20181221233252/http://www.math.mcgill.ca/triples/Barr-Wells-ctcs.pdf) - Michael Barr, Charles Wells
@@ -258,7 +254,7 @@ All resources are freely available except those with a 💲 icon.
 * 📝 [Basic Concepts of Enriched Category Theory](http://www.tac.mta.ca/tac/reprints/articles/10/tr10abs.html) - G. M. Kelley
 * 📝 [Abstract and Concrete Categories: The Joy of Cats](http://www.tac.mta.ca/tac/reprints/articles/17/tr17abs.html) - Jiri Adamek, Horst Herrlich, George Strecker
 * 📝 [Seven Sketches in Compositionality: An Invitation to Applied Category Theory](http://math.mit.edu/~dspivak/teaching/sp18/7Sketches.pdf) - Brendan Fong and David I. Spivak (MIT)
-* 📝 [Category Theory in Context](http://www.math.jhu.edu/~eriehl/context/) - Emily Riehl (John Hopkins University)
+* 📝 [Category Theory in Context](https://math.jhu.edu/~eriehl/context/) - Emily Riehl (John Hopkins University)
 
 ### Type Theory
 * 📝 [Proofs and Types](http://www.paultaylor.eu/stable/prot.pdf) - Jean-Yves Girard
@@ -274,12 +270,11 @@ All resources are freely available except those with a 💲 icon.
 
 * 📝 [Surreal Numbers - How two ex-students turned on to pure mathematics and found total happiness](http://www.math.harvard.edu/~knill/teaching/mathe320_2015_fall/blog15/surreal1.pdf) - D. E. Knuth
 * 📝 [Surreal Numbers and Games](http://web.mit.edu/sp.268/www/2010/surreal.pdf)
-* 📝 [Conway names, the simplicity hierarchy and the surreal number tree](http://www.ohio.edu/people/ehrlich/ConwayNames.pdf) - Philip Ehrlich
 
 
 ## Number Theory
 
-* 📝 [Elementary Number Theory: Primes, Congruences, and Secrets](http://wstein.org/ent/ent.pdf) - William Stein
+* 📝 [Elementary Number Theory: Primes, Congruences, and Secrets](https://wstein.org/ent/ent.pdf) - William Stein
 * 📝 [Elementary Number Theory](http://math.utoledo.edu/~codenth/Spring_13/3200/ENT-books/Elementary_Number_Theory-Clark.pdf) - W. Edwin Clark (University of South Florida)
 * 📝 [A Course on Number Theory](http://www.maths.qmul.ac.uk/~pjc/notes/nt.pdf) - Peter J. Cameron
 * 📝 [A Computational Introduction to Number Theory and Algebra](http://shoup.net/ntb/ntb-v2.pdf) - Victor Shoup
@@ -290,13 +285,13 @@ All resources are freely available except those with a 💲 icon.
 ### Algebraic Number Theory
 
 * 📝 [Introduction to Algebraic Number Theory](https://feog.github.io/ANT10.pdf) - F. Oggier
-* 📝 [Algebraic Number Theory](http://www.jmilne.org/math/CourseNotes/ANT.pdf) - J.S. Milne
-* 📝 [Algebraic Number Theory Course Notes](http://people.math.gatech.edu/~mbaker/pdf/ANTBook.pdf) - Matthew Baker (Georgia Tech)
-* 📝 [A Course In Algebraic Number Theory](http://www.math.uiuc.edu/~r-ash/ANT.html) - Robert Ash
+* 📝 [Algebraic Number Theory](https://www.jmilne.org/math/CourseNotes/ANT.pdf) - J.S. Milne
+* 📝 [Algebraic Number Theory Course Notes](https://mattbaker.blog/) - Matthew Baker (Georgia Tech)
+* 📝 [A Course In Algebraic Number Theory](https://faculty.math.illinois.edu/~r-ash/ANT.html) - Robert Ash
 
 ### Analytic Number Theory
 
-* 📝 [Introduction to Analytic Number Theory](http://www.math.uiuc.edu/~hildebr/ant/main.pdf) - A.J. Hildebrand (University of Illinois)
+* 📝 [Introduction to Analytic Number Theory](https://faculty.math.illinois.edu/~hildebr/ant/main.pdf) - A.J. Hildebrand (University of Illinois)
 * 📝 [Elements of Analytic Number Theory](http://math.nsc.ru/~vdovin/lectures/numth_eng.pdf) - P. S. Kolesnikov, E. P. Vdovin (Novosibirsk)
 * 📝 [Analytic Number Theory](http://www.mathematik.uni-muenchen.de/~forster/v/ann/annth_all.pdf) - Otto Forster (LMU Munich)
 * 📝 [Analytic Number Theory - Lecture Notes based on Davenport’s book](http://www2.math.uu.se/~astrombe/analtalt08/www_notes.pdf) - Andreas Strömbergsson
@@ -310,24 +305,22 @@ All resources are freely available except those with a 💲 icon.
 * 📝 [Second Course in Algebra](http://djm.cc/library/Second_Algebra_Hawkes_Luby_Touton_edited.pdf) - Herbert E. Hawkes, William A. Luby, Frank C. Touton (1911)
 * 📝 [Algebra: An Elementary Text-Book, Part I](http://djm.cc/library/Algebra_Elementary_Text-Book_Part_I_Chrystal_edited.pdf) - G. Chrystal (1904)
 * 📝 [Algebra: An Elementary Text-Book, Part II](http://djm.cc/library/Algebra_Elementary_Text-Book_Part_II_Chrystal_edited02.pdf) - G. Chrystal (1900)
-* 📝 [Understanding Algebra](https://jamesbrennan.org/algebra) - James W. Brennan
+* 📝 [Understanding Algebra](https://jamesbrennan.org/algebra/) - James W. Brennan
 
 ### Abstract Algebra
 
-* 📝 [Introduction to Abstract Algebra](https://zodml.org/sites/default/files/Introduction_to_Abstract_Algebra_0.pdf) - D. S. Malik, John N. Mordeson, M.K. Sen (Creighton University)
 * 📝 [Introduction to Modern Algebra](http://aleph0.clarku.edu/~djoyce/ma225/algebra.pdf) - David Joyce (Clark University)
 * 📝 [Algebraic Methods](https://feog.github.io/AA11.pdf) - F. Oggier
 * 📝 [Abstract Algebra : Theory and Applications](http://abstract.ups.edu/download/aata-20150812.pdf) - Thomas W. Judson, Robert A. Beezer (Austin State University)
-* 📝 [An Undergraduate Course in Abstract Algebra](http://www.maths.usyd.edu.au/u/bobh/UoS/rfwhole.pdf) - Robert Howlett
-* 📝 [Elements of Abstract and Linear Algebra](http://www.math.miami.edu/~ec/book) - E.H. Connell (University of Miami)
-* 📝 [Abstract Algebra: The Basic Graduate Year](http://www.math.uiuc.edu/~r-ash/Algebra.html) - Robert Ash
+* 📝 [An Undergraduate Course in Abstract Algebra](https://www.maths.usyd.edu.au/u/bobh/UoS/rfwhole.pdf) - Robert Howlett
+* 📝 [Elements of Abstract and Linear Algebra](https://www.math.miami.edu/~ec/book/) - E.H. Connell (University of Miami)
+* 📝 [Abstract Algebra: The Basic Graduate Year](https://faculty.math.illinois.edu/~r-ash/Algebra.html) - Robert Ash
 * 📝 [Abstract Algebra: Harvard Extension (Archived)](https://web.archive.org/web/20150528171650/extension.harvard.edu/open-learning-initiative/abstract-algebra) - Benedict Gross
 * 📝 [Abstract Algebra: Harvard Extension Videos](https://www.youtube.com/playlist?list=PLA58AC5CABC1321A3) - Benedict Gross
 
 ### Group Theory
 
-* 📝 [Notes on Group Theory](https://www2.bc.edu/mark-reeder/Groups.pdf) - Mark Reeder
-* 📝 [Group Theory](http://www.jmilne.org/math/CourseNotes/GT.pdf) - J.S. Milne
+* 📝 [Group Theory](https://www.jmilne.org/math/CourseNotes/GT.pdf) - J.S. Milne
 * 📝 [Notes on Finite Group Theory](http://www.maths.qmul.ac.uk/~pjc/notes/gt.pdf) - Peter J. Cameron
 * 📝 [Group Theory](http://www.cns.gatech.edu/GroupTheory/index.html) - Pedrag Civitanovic
 
@@ -335,8 +328,8 @@ All resources are freely available except those with a 💲 icon.
 
 * 📝 [Fundamentals of Linear Algebra](http://www.math.ubc.ca/~carrell/NB.pdf) - James B. Carrell
 * 📝 [Linear Algebra and Matrices](https://web.archive.org/web/20140824074655/http://mathstat.helsinki.fi/~fluch/linear_algebra_1-sp07/la1.pdf) - Martin Fluch
-* 📝 [Vector Space Theory](http://www.maths.usyd.edu.au/u/bobh/UoS/MATH2902/vswhole.pdf) - Robert Howlett
-* 📝 [Linear Algebra](http://joshua.smcvt.edu/linearalgebra) - Jim Hefferon
+* 📝 [Vector Space Theory](https://www.maths.usyd.edu.au/u/bobh/UoS/MATH2902/vswhole.pdf) - Robert Howlett
+* 📝 [Linear Algebra](https://joshua.smcvt.edu/linearalgebra/) - Jim Hefferon
 * 📝 [MIT OpenCourseWare Lectures on Linear Algebra (18.06) as Jupyter Notebooks](https://github.com/juanklopper/MIT_OCW_Linear_Algebra_18_06) - Juan Klopper
 * 📝 [Elementary Linear Algebra](http://www.numbertheory.org/book/) - Keith Matthews
 * 📝 [A First Courses in Linear Algebra](http://linear.ups.edu/) - Rob Breezer
@@ -357,7 +350,7 @@ All resources are freely available except those with a 💲 icon.
 ### Galois Theory
 
 * 📝 [An Introduction to Galois Theory](http://www.maths.gla.ac.uk/~ajb/dvi-ps/Galois.pdf) - Andrew Baker (University of Glasgow)
-* 📝 [Fields and Galois Theory](http://www.jmilne.org/math/CourseNotes/FT.pdf) - J.S. Milne
+* 📝 [Fields and Galois Theory](https://www.jmilne.org/math/CourseNotes/FT.pdf) - J.S. Milne
 * 📝 [Galois theory](http://homepages.warwick.ac.uk/~masda/MA3D5/Galois.pdf) - Miles Reid
 * 📝 [Galois Theory](https://eclass.uoa.gr/modules/document/file.php/MATH594/Stewart%20Galois%204th%20edition.pdf) - Ian Stewart
 * 📝 [Galois Theory](https://arxiv.org/pdf/2408.07499) — Tom Leinster (University of Edinburgh)
@@ -369,10 +362,10 @@ All resources are freely available except those with a 💲 icon.
 ## Combinatorics
 
 * 📝 [Basic Combinatorics](http://web.math.utk.edu/~wagner/papers/comb.pdf) - Carl G. Wagner (University of Tennessee)
-* 📝 [Applied Combinatorics](http://people.math.gatech.edu/~trotter/book.pdf) - Mitchel T. Keller, William T. Trotter
+* 📝 [Applied Combinatorics](https://people.math.gatech.edu/~trotter/book.pdf) - Mitchel T. Keller, William T. Trotter
 * 📝 [Notes on Combinatorics](http://www.maths.qmul.ac.uk/~pjc/notes/comb.pdf) - Peter J. Cameron
 * 📝 [Analytic Combinatorics](http://algo.inria.fr/flajolet/Publications/book.pdf) - Philippe Flajolet, Robert Sedgewick
-* 📝 [generatingfunctionology](http://www.math.upenn.edu/~wilf/DownldGF.html) - Herbert Wilf
+* 📝 [generatingfunctionology](https://www2.math.upenn.edu/~wilf/DownldGF.html) - Herbert Wilf
 
 ### Graph Theory
 
@@ -384,7 +377,7 @@ All resources are freely available except those with a 💲 icon.
 ## Geometry and Topology
 
 * 📝 [Fundamentals of Geometry](http://polly.phys.msu.ru/~belyaev/geometry.pdf) - Oleg A. Belyaev
-* 📝 [A=B](https://www.math.upenn.edu/~wilf/AeqB.html) - M. Petkovsek, H. Wilf, D. Zeilberger
+* 📝 [A=B](https://www2.math.upenn.edu/~wilf/AeqB.html) - M. Petkovsek, H. Wilf, D. Zeilberger
 * 📝 [Elements](http://aleph0.clarku.edu/~djoyce/java/elements/toc.html) - Euclid
 * 📝 [Euclid's Elements Redux](http://starrhorse.com/euclid/) - Daniel Callahan
 * 📝 [Mathematical Illustrations](http://www.math.ubc.ca/~cass/graphics/manual/) - Bill Casselman
@@ -398,10 +391,10 @@ All resources are freely available except those with a 💲 icon.
 
 * 📝 [Introduction to Differential Geometry](https://people.math.ethz.ch/~salamon/PREPRINTS/diffgeo.pdf) - Joel W. Robbin, Dietmar A. Salamon
 * 📝 [Notes on Differential Geometry and Lie Groups](https://www.cis.upenn.edu/~jean/gbooks/manif.html) - Jean Gallier (University of Pennsylvania)
-* 📝 [Topics in Differential Geometry](http://www.mat.univie.ac.at/~michor/dgbook.pdf) - Peter W. Michor
-* 📝 [Lectures on Differential Geometry](http://mysite.science.uottawa.ca/rossmann/Differential%20Geometry%20book_files/Diffgeo.pdf) - Wulf Rossmann
-* 📝 [An Introduction to Riemannian Geometry](http://www.matematik.lu.se/matematiklu/personal/sigma/Riemann.pdf) - Sigmundur Gudmundsson (Lund University)
-* 📝 [The Geometry and Topology of Three-Manifolds](http://msri.org/publications/books/gt3m/) - W. Thurston
+* 📝 [Topics in Differential Geometry](https://www.mat.univie.ac.at/~michor/dgbook.pdf) - Peter W. Michor
+* 📝 [Lectures on Differential Geometry](https://mysite.science.uottawa.ca/rossmann/Differential%20Geometry%20book_files/Diffgeo.pdf) - Wulf Rossmann
+* 📝 [An Introduction to Riemannian Geometry](https://www.maths.lth.se/matematiklu/personal/sigma/Riemann.pdf) - Sigmundur Gudmundsson (Lund University)
+* 📝 [The Geometry and Topology of Three-Manifolds](http://library.msri.org/books/gt3m/) - W. Thurston
 * 📝 [Semi-Riemann Geometry and General Relativity](http://www.math.harvard.edu/~shlomo/docs/semi_riemannian_geometry.pdf) - Shlomo Sternberg
 * 📝 [Discrete Differential Geometry](http://www.cs.cmu.edu/~kmcrane/Projects/DDG/paper.pdf) - Keenan Crane
 
@@ -410,9 +403,9 @@ All resources are freely available except those with a 💲 icon.
 * 📝 [A Brief Introduction to Algebraic Geometry](https://ksda.ccny.cuny.edu/PostedPapers/rickksda1107.pdf) - R.C. Churchill
 * 📝 [Introduction to Algebraic Geometry](http://www.math.lsa.umich.edu/~idolga/631.pdf) - Igor V. Dolgachev
 * 📝 [Foundations of Algebraic Geometry](http://math.stanford.edu/~vakil/216blog/FOAGjun1113public.pdf) - Ravi Vakil
-* 📝 [Algebraic Geometry](http://www.cis.upenn.edu/~jean/algeoms.pdf) - Jean Gallier, Stephen S. Shatz (University of Pennsylvania)
-* 📝 [Algebraic Geometry](http://www.jmilne.org/math/CourseNotes/AG.pdf) - J.S. Milne
-* 📝 [Algebraic Geometry](http://www.mathematik.uni-kl.de/~gathmann/class/alggeom-2002/main.pdf) - Andreas Gathmann (University of Kaiserslautern)
+* 📝 [Algebraic Geometry](https://www.cis.upenn.edu/~jean/algeoms.pdf) - Jean Gallier, Stephen S. Shatz (University of Pennsylvania)
+* 📝 [Algebraic Geometry](https://www.jmilne.org/math/CourseNotes/AG.pdf) - J.S. Milne
+* 📝 [Algebraic Geometry](https://www.mathematik.uni-kl.de/~gathmann/class/alggeom-2002/main.pdf) - Andreas Gathmann (University of Kaiserslautern)
 * 📝 [The Stacks Project](https://stacks.math.columbia.edu/) - Maintained by Aise Johan de Jong (Columbia)
 
 ### Algebraic Statistics
@@ -423,24 +416,21 @@ All resources are freely available except those with a 💲 icon.
 
 ### Topology
 
-* 📝 [Elementary Applied Topology](https://www.math.upenn.edu/~ghrist/notes.html) - Robert Ghrist (UPenn)
-* 📝 [Introduction to Topology](http://www.math.colostate.edu/~renzo/teaching/Topology10/Notes.pdf)
-* 📝 [Introduction to Topology](http://www.math.bme.hu/~kalex/Teaching/Spring10/Topology/TopNotes_Spring10.pdf) - Alex Küronya
-* 📝 [Introductory Topology](http://www.math.clemson.edu/~jimlb/Teaching/2009-10/Math986/Topology.pdf) - Jim L. Brown
+* 📝 [Elementary Applied Topology](https://www2.math.upenn.edu/~ghrist/notes.html) - Robert Ghrist (UPenn)
+* 📝 [Introduction to Topology](https://www.math.colostate.edu/~renzo/teaching/Topology10/Notes.pdf)
+* 📝 [Introduction to Topology](http://math.bme.hu/~kalex/Teaching/Spring10/Topology/TopNotes_Spring10.pdf) - Alex Küronya
 * 📝 [General Topology](http://webusers.imj-prg.fr/~pierre.schapira/lectnotes/Topo.pdf) - Pierre Schapira (Paris VI University)
 * 📝 [Elementary Topology Problem Textbook](http://www.pdmi.ras.ru/~olegviro/topoman/eng-book-nopfs.pdf)
-* 📝 [General Topology](http://www.math.ku.dk/~moller/e03/3gt/notes/gtnotes.pdf) - Jesper M. Møller
+* 📝 [General Topology](http://web.math.ku.dk/~moller/e03/3gt/notes/gtnotes.pdf) - Jesper M. Møller
 * 📝 [Topology Topics](http://mathonline.wikidot.com/topology)
 
 ### Algebraic Topology
 
-* 📝 [Algebraic Topology](http://www.math.cornell.edu/~hatcher/AT/AT.pdf) - Allen Hatcher
+* 📝 [Algebraic Topology](https://pi.math.cornell.edu/~hatcher/AT/AT.pdf) - Allen Hatcher
 * 📝 [A Concise Course in Algebraic Topology](http://www.math.uchicago.edu/~may/CONCISE/ConciseRevised.pdf) - J. P. May
 * 📝 [Introduction to Algebraic Topology](http://www.math.muni.cz/~cadek/at/at.pdf) - Martin Cadek
 * 📝 [Algebra and Topology](http://webusers.imj-prg.fr/~pierre.schapira/lectnotes/AlTo.pdf) - Pierre Schapira (Paris VI University)
-* 📝 [Lecture Notes in Algebraic Topology](http://www.indiana.edu/~jfdavis/teaching/m623/book.pdf) - James F. Davis, Paul Kirk (Indiana University)
-* 📝 [Algebraic Topology](https://www.ma.utexas.edu/ibl1/courses/resources/12_15_07_grad_alg_top_mooremethod.pdf) - Michael Starbird
-* 📝 [Lecture Notes on Algebraic Topology](http://www.math.nus.edu.sg/~matwujie/ma5209.pdf) - Jie Wu
+* 📝 [Algebraic Topology](https://web.ma.utexas.edu/ibl1/courses/resources/12_15_07_grad_alg_top_mooremethod.pdf) - Michael Starbird
 
 
 ## Analysis
@@ -448,11 +438,10 @@ All resources are freely available except those with a 💲 icon.
 ### Real Analysis
 
 * 📝 [MIT OpenCourseWare Lectures on Calculus](https://ocw.mit.edu/resources/res-18-001-calculus-online-textbook-spring-2005/textbook/) - G. Strang
-* 📝 [Elementary Calculus: An Approach Using Infinitesimals](http://www.math.wisc.edu/~keisler/calc.html) - Professor H. Jerome Keisler
+* 📝 [Elementary Calculus: An Approach Using Infinitesimals](https://people.math.wisc.edu/~keisler/calc.html) - Professor H. Jerome Keisler
 * 📝 [An Introduction to Real Analysis](https://www.math.ucdavis.edu/~hunter/intro_analysis_pdf/intro_analysis.pdf) - John K. Hunter (University of California at Davis)
 * 📝 [Introduction to Real Analysis](http://ramanujan.math.trinity.edu/wtrench/texts/TRENCH_REAL_ANALYSIS.PDF) - William F. Trench (Trinity University, Texas)
-* 📝 [Basic Analysis: Introduction to Real Analysis](http://www.jirka.org/ra/realanal.pdf) - Jiří Lebl
-* 📝 [Elementary Real Analysis](http://prac.im.pwr.wroc.pl/~kwasnicki/pl/stuff/tbb-hyper.pdf) - Thomson, Bruckner
+* 📝 [Basic Analysis: Introduction to Real Analysis](https://www.jirka.org/ra/realanal.pdf) - Jiří Lebl
 * 📝 [Lecture Notes in Real Analysis](http://ms.mcmaster.ca/~sawyer/Publications/Real_Analysis.pdf) - Eric T. Sawyer (McMaster University)
 * 📝 [Real Analysis](http://math.harvard.edu/~ctm/papers/home/text/class/harvard/212a/course/course.pdf) - C. McMullen
 * 📝 [Real Analysis for Graduate Students](http://bass.math.uconn.edu/3rd.pdf) - Richard F. Bass
@@ -460,7 +449,7 @@ All resources are freely available except those with a 💲 icon.
 * 📝 [Mathematical Analysis Vol I](http://www.trillia.com/zakon-analysisI.html) - Elias Zakon
 * 📝 [Mathematical Analysis Vol II](http://www.trillia.com/zakon-analysisII.html) - Elias Zakon
 * 📝 [Advanced Calculus](http://www.math.harvard.edu/~shlomo/docs/Advanced_Calculus.pdf) - Lynn Loomis, Schlomo Sternberg
-* 📝 [ Analysis of Functions of a Single Variable](http://spot.colorado.edu/~baggett/analysis.html) - Lawerence Baggett
+* 📝 [ Analysis of Functions of a Single Variable](https://spot.colorado.edu/~baggett/analysis.html) - Lawerence Baggett
 * 📝 [The Calculus of Functions of Several Variables](http://www.synechism.org/wp/the-calculus-of-functions-of-several-variables/) - Dan Sloughter
 * 📝 [A ProblemText in Advanced Calculus](http://web.pdx.edu/~erdman/PTAC/problemtext_pdf.pdf) - John M. Erdman
 * 📝 [Calculus and Linear Algebra. Vol. 1](http://hdl.handle.net/2027/spo.5597602.0001.001) - Wilfred Kaplan, Donald J. Lewis
@@ -474,44 +463,41 @@ All resources are freely available except those with a 💲 icon.
 
 ### Harmonic Analysis
 
-* 📝 [Harmonic Analysis Lecture Notes](http://www.math.uiuc.edu/~laugesen/545/545Lectures.pdf) - Richard S. Laugesen (University of Illinois at Urbana–Champaign)
-* 📝 [Harmonic Analysis](http://www.math.uchicago.edu/~schlag/harmonicnotes.pdf) - W. Schlag
+* 📝 [Harmonic Analysis Lecture Notes](https://faculty.math.illinois.edu/~laugesen/545/545Lectures.pdf) - Richard S. Laugesen (University of Illinois at Urbana–Champaign)
 * 📝 [Lecture Notes: Fourier Transform and its Applications](https://see.stanford.edu/materials/lsoftaee261/book-fall-07.pdf) - Brad Osgood
 * 📝 [Fourier Analysis](http://www.reed.edu/physics/courses/Physics331.f08/pdf/Fourier.pdf) - Lucas Illing
-* 📝 [Mathematics of the Discrete Fourier Transform (DFT) with Audio Applications](https://ccrma.stanford.edu/~jos/mdft) - Julius O. Smith III (Stanford University)
+* 📝 [Mathematics of the Discrete Fourier Transform (DFT) with Audio Applications](https://ccrma.stanford.edu/~jos/mdft/) - Julius O. Smith III (Stanford University)
 
 ### Complex Analysis
 
 * 📝 [Introduction to Complex Analysis](https://mtaylor.web.unc.edu/wp-content/uploads/sites/16915/2018/04/complex.pdf) - Michael Taylor
-* 📝 [An Introduction to Complex Analysis and Geometry](http://www.math.uiuc.edu/~jpda/jpd-complex-geometry-book-5-refs-bip.pdf) - John P. D'Angelo (University of Illinois)
+* 📝 [An Introduction to Complex Analysis and Geometry](https://faculty.math.illinois.edu/~jpda/jpd-complex-geometry-book-5-refs-bip.pdf) - John P. D'Angelo (University of Illinois)
 * 📝 [A First Course in Complex Analysis](http://math.sfsu.edu/beck/papers/complex.pdf) - Matthias Beck, Gerald Marchesi, Dennis Pixton, Lucas Sabalka
 * 📝 [A Guide to Complex Variables](http://www.math.wustl.edu/~sk/books/guide.pdf) - Steven G. Krantz
-* 📝 [Complex Analysis](http://www.maths.manchester.ac.uk/~cwalkden/complex-analysis/complex_analysis.pdf) - Charles Walkden
-* 📝 [Complex Analysis](http://www.math.ku.dk/noter/filer/koman-12.pdf) - Christian Berg
+* 📝 [Complex Analysis](https://personalpages.manchester.ac.uk/staff/charles.walkden/) - Charles Walkden
+* 📝 [Complex Analysis](http://web.math.ku.dk/noter/filer/koman-12.pdf) - Christian Berg
 * 📝 [Complex Variables](http://people.math.sc.edu/girardi/m7034/book/AshComplexVariablesWithHyperlinks.pdf) - R. B. Ash, W.P. Novinger
-* 📝 [Complex Analysis](http://www.maths.lth.se/matematiklu/personal/olofsson/CompHT06.pdf) - Christer Bennewitz
+* 📝 [Complex Analysis](https://www.maths.lth.se/matematiklu/personal/olofsson/CompHT06.pdf) - Christer Bennewitz
 * 📝 [Complex Analysis](https://web.archive.org/web/20150620124453/https://www.math.washington.edu/~marshall/math_536/Notes.pdf) - Donald E. Marshall
 * 📝 [A Concise Course in Complex Analysis and Riemann Surfaces](https://gauss.math.yale.edu/~ws442/complex.pdf) - Wilhelm Schlag
-* 📝 [Complex Analysis](http://people.math.gatech.edu/%7Ecain/winter99/complex.html) - G. Cain (Georgia Tech)
+* 📝 [Complex Analysis](https://people.math.gatech.edu/~cain/winter99/complex.html) - G. Cain (Georgia Tech)
 * 📝 [Complex Analysis](https://complex-analysis.com/) - Juan Carlos Ponce Campuzano
 
 ### Functional Analysis
 
 * 📝 [An Introduction to Functional Analysis](https://www.math.uwaterloo.ca/~lwmarcou/notes/pmath453.pdf) - Laurent W. Marcoux (University of Waterloo)
-* 📝 [Functional Analysis: Lecture Notes](http://users.math.msu.edu/users/jeffrey/920/920notes.pdf) - Jeff Schenker (Michigan State University)
+* 📝 [Functional Analysis: Lecture Notes](https://users.math.msu.edu/users/schenke6/920/920notes.pdf) - Jeff Schenker (Michigan State University)
 * 📝 [Functional Analysis Lecture Notes](https://archive.org/details/TB_Ward___Functional_analysis_lecture_notes) - T.B. Ward (University of East Anglia)
-* 📝 [Functional Analysis](http://www.maths.lancs.ac.uk/~belton/www/notes/fa_notes.pdf) - Alexander C. R. Belton
+* 📝 [Functional Analysis](https://www.maths.lancs.ac.uk/~belton/www/notes/fa_notes.pdf) - Alexander C. R. Belton
 * 📝 [Topics in Real and Functional Analysis](https://www.mat.univie.ac.at/~gerald/ftp/book-fa/fa.pdf) - Gerald Teschl
-* 📝 [Functional Analysis](http://www2.math.ou.edu/~cremling/teaching/lecturenotes/fa-new/LN-I.pdf) - Christian Remling
 * 📝 [Theory of Functions of a Real Variable](http://www.math.harvard.edu/~shlomo/docs/Real_Variables.pdf) - Shlomo Sternberg
-* 📝 [Functional Analysis](http://spot.colorado.edu/~baggett/functional.html) - Lawerence Baggett
+* 📝 [Functional Analysis](https://spot.colorado.edu/~baggett/functional.html) - Lawerence Baggett
 
 ### Measure Theory
 
 * 📝 [An Introduction to Measure Theory](https://terrytao.files.wordpress.com/2012/12/gsm-126-tao5-measure-book.pdf) - Terence Tao (UCLA)
 * 📝 [Lecture Notes on Measure Theory and Functional Analysis](http://www.mat.uniroma2.it/~cannarsa/cam_0607.pdf) - P. Cannarsa, T. D’Aprile
 * 📝 [Lecture Notes in Measure Theory](http://www.math.chalmers.se/~borell/MeasureTheory.pdf) - Christer Borell
-* 📝 [A Crash Course on the Lebesgue Integral and Measure Theory](http://www.gold-saucer.org/math/lebesgue/lebesgue.pdf) - Steve Cheng
 * 📝 [Measure Theory](https://www.math.ucdavis.edu/~hunter/measure_theory/measure_notes.pdf) - John K. Hunter (University of California at Davis)
 * 📝 [Measure and Integration](https://people.math.ethz.ch/~salamon/PREPRINTS/measure.pdf) - Dietmar A. Salamon (ETH Zürich)
 * 📝 [Lecture notes: Measure Theory](http://www.math.ucsd.edu/~bdriver/240-00-01/Lecture_Notes/measurep.pdf) - Bruce K. Driver
@@ -520,14 +506,14 @@ All resources are freely available except those with a 💲 icon.
 
 * 📝 [Difference Equations To Differential Equations](http://www.synechism.org/wp/difference-equations-to-differential-equations/) - Dan Sloughter
 * 📝 [Ordinary Differential Equation](https://www.math.uni-bielefeld.de/~grigor/odelec2008.pdf) - Alexander Grigorian (University of Bielefeld)
-* 📝 [Ordinary Differential Equations: Lecture Notes](http://www.cs.bgu.ac.il/~leonid/ode_bio_files/Ionascu_LectNotes.pdf) - Eugen J. Ionascu
+* 📝 [Ordinary Differential Equations: Lecture Notes](https://www.cs.bgu.ac.il/~leonid/ode_bio_files/Ionascu_LectNotes.pdf) - Eugen J. Ionascu
 * 📝 [Ordinary Differential Equations](http://www.math.lmu.de/~philip/publications/lectureNotes/ODE.pdf) - Peter Philip
-* 📝 [Ordinary Differential Equations](http://users.math.msu.edu/users/gnagy/teaching/ode.pdf) - Gabriel Nagy
-* 📝 [Ordinary Differential Equations and Dynamical Systems](http://www.mat.univie.ac.at/~gerald/ftp/book-ode/ode.pdf) - Gerald Teschl
+* 📝 [Ordinary Differential Equations](https://users.math.msu.edu/users/gnagy/teaching/ode.pdf) - Gabriel Nagy
+* 📝 [Ordinary Differential Equations and Dynamical Systems](https://www.mat.univie.ac.at/~gerald/ftp/book-ode/ode.pdf) - Gerald Teschl
 * 📝 [Notes on Differential Equations](http://leipper.org/manuals/zip-fill/dn-difeq-notes.pdf) - Bob Terrell
-* 📝 [Elementary Differential Equations](http://digitalcommons.trinity.edu/mono/8/) - William F. Trench
-* 📝 [Elementary Differential Equations With Boundary Value Problems](http://digitalcommons.trinity.edu/mono/9/) - William F. Trench
-* 📝 [Notes on Diffy Qs: Differential Equations for Engineers](http://www.jirka.org/diffyqs/) - Jiří Lebl
+* 📝 [Elementary Differential Equations](https://digitalcommons.trinity.edu/mono/8/) - William F. Trench
+* 📝 [Elementary Differential Equations With Boundary Value Problems](https://digitalcommons.trinity.edu/mono/9/) - William F. Trench
+* 📝 [Notes on Diffy Qs: Differential Equations for Engineers](https://www.jirka.org/diffyqs/) - Jiří Lebl
 * 📝 [Differential Equations](http://djm.cc/library/Differential_Equations_Phillips_edited.pdf) - H. B. Phillips (1922)
 
 ### Partial Differential Equations
@@ -546,13 +532,13 @@ All resources are freely available except those with a 💲 icon.
 
 ### Probability Theory
 
-* 📝 [Introduction to Probability](https://www.dartmouth.edu/~chance/teaching_aids/books_articles/probability_book/amsbook.mac.pdf) - Charles M. Grinstead, J. Laurie Snell
+* 📝 [Introduction to Probability](https://chance.dartmouth.edu) - Charles M. Grinstead, J. Laurie Snell
 * 📝 [Introduction to Probability](http://vfu.bg/en/e-Learning/Math--Bertsekas_Tsitsiklis_Introduction_to_probability.pdf) - Dimitri P. Bertsekas, John N. Tsitsiklis (MIT)
 * 📝 [A Short Introduction to Probability](http://www.maths.uq.edu.au/~kroese/asitp.pdf) - Dirk P. Kroese (University of Queensland)
 * 📝 [Probability: Theory and Examples](https://www.math.duke.edu/~rtd/PTE/PTE4_1.pdf) - Rick Durrett
 * 📝 [Probability and Statistics Cookbook](https://github.com/mavam/stat-cookbook/releases/download/0.2.3/stat-cookbook.pdf) - Matthias Vallentin (UC Berkeley)
 * 📝 [The Only Probability Cheatsheet You'll Ever Need](http://www.wzchen.com/probability-cheatsheet/) - William Chen
-* 📝 [An Introduction to Probability and Random Processes](http://www.ellerman.org/Davids-Stuff/Maths/Rota-Baclawski-Prob-Theory-79.pdf) - Gian-Carlo Rota, Kenneth Baclawski
+* 📝 [An Introduction to Probability and Random Processes](https://ellerman.org/Davids-Stuff/Maths/Rota-Baclawski-Prob-Theory-79.pdf) - Gian-Carlo Rota, Kenneth Baclawski
 * 📝 [Foundations of Constructive Probability Theory](https://arxiv.org/pdf/1906.01803.pdf) - Yuen-Kwok Chan
 
 ### Statistics
@@ -561,11 +547,10 @@ All resources are freely available except those with a 💲 icon.
 * 📝 [Introduction to Statistics and Data Analysis for Physicists](http://www-library.desy.de/preparch/books/vstatmp_engl.pdf) - Gerhard Bohm, Günter Zech
 * 📝 [Probability and Mathematical Statistics](http://www.iiserpune.ac.in/~ayan/MTH201/Sahoo_textbook.pdf) - Prasanna Sahoo (University of Louisville)
 * 📝 [Lectures on Statistics](http://math.arizona.edu/~faris/stat.pdf) - William G. Faris
-* 📝 [Statistical Theory](http://pages.pomona.edu/~ajr04747/Fall2009/Math152/Notes/Math152NotesFall09.pdf) - Adolfo J. Rumbos
+* 📝 [Statistical Theory](https://pages.pomona.edu/~ajr04747/Fall2009/Math152/Notes/Math152NotesFall09.pdf) - Adolfo J. Rumbos
 * 📝 [Theory of Statistics](http://mason.gmu.edu/~jgentle/books/MathStat.pdf) - James E. Gentle (George Mason University)
 * 📝 [Theory of Statistics](http://math.arizona.edu/~jwatkins/notests.pdf) - Joseph C. Watkins (University of Arizona)
 * 📝 [Glossary of Data Modeling](https://web.archive.org/web/20130523134625/http://www.aiaccess.net/e_gm.htm) - AI Access
-* 📝 [Statistics Papers](http://www.ats.ucla.edu/stat/papers/) - List of statistics papers curated by the Institute for Digital Research and Education (IDRE) at UCLA on methods such as bootstrap and factor invariance.
 * 📝 [NIST Handbook of Statistical Methods](http://itl.nist.gov/div898/handbook/index.htm) - Resource on practical statistics directed towards scientists and engineers.
 * 📝 [Concepts and Applications of Inferential Statistics](http://vassarstats.net/textbook/) - Richard Lowry
 * 📝 [Rough set data analysis: A road to non-invasive knowledge discovery](http://www.cosc.brocku.ca/~duentsch/papers/methprimer2.html) - Ivo Düntsch, Günther Gediga
@@ -577,10 +562,9 @@ All resources are freely available except those with a 💲 icon.
 
 ### Statistical Learning
 
-* 📝 [An Introduction to Statistical Learning with Applications in R](http://www-bcf.usc.edu/~gareth/ISL/ISLR%20First%20Printing.pdf) - Gareth James, Daniela Witten, Trevor Hastie, Robert Tibshirani
+* 📝 [An Introduction to Statistical Learning with Applications in R](http://faculty.marshall.usc.edu/gareth-james/) - Gareth James, Daniela Witten, Trevor Hastie, Robert Tibshirani
 * 📝 [The Elements of Statistical Learning](http://web.stanford.edu/~hastie/Papers/ESLII.pdf) - Trevor Hastie, Robert Tibshirani, Jerome Friedman
 * 📝 [Statistical Learning Theory](https://web.stanford.edu/class/cs229t/notes.pdf) - Percy Liang
-* 📝 [Reinforcement Learning: An Introduction](https://webdocs.cs.ualberta.ca/~sutton/book/bookdraft2016sep.pdf) - Richard S. Sutton, Andrew G. Barto
 
 ### Stochastic processes
 
@@ -588,7 +572,7 @@ All resources are freely available except those with a 💲 icon.
 * 📝 [Probability and Stochastic Processes with Applications](http://www.math.harvard.edu/~knill/teaching/math144_1994/probability.pdf) - Oliver Knill (Harvard University)
 * 📝 [Stochastic Processes](http://statweb.stanford.edu/~adembo/math-136/nnotes.pdf) - Amir Dembo (Stanford University)
 * 📝 [Lecture Notes on Stochastic Processes](http://www.mi.fu-berlin.de/wiki/pub/CompMolBio/MarkovKetten15/stochastic_processes_2011.pdf) - Frank Noé, Bettina Keller and Jan-Hendrik Prinz (Freie Universität Berlin)
-* 📝 [Introduction to Stochastic Processes - Lecture Notes](https://www.ma.utexas.edu/users/gordanz/notes/introduction_to_stochastic_processes.pdf) - Gordan Žitković (University of Texas)
+* 📝 [Introduction to Stochastic Processes - Lecture Notes](https://web.ma.utexas.edu/users/gordanz/notes/introduction_to_stochastic_processes.pdf) - Gordan Žitković (University of Texas)
 * 📝 [Applied Stochastic Processes in science and engineering](https://www.math.uwaterloo.ca/~mscott/Little_Notes.pdf) - Matt Scott (University of Waterloo)
 * 📝 [An Introduction to Stochastic Processes in Continuous Time](http://www.math.leidenuniv.nl/~spieksma/colleges/sp-master/sp-hvz1.pdf) - Flora Spieksma (Leiden University)
 * 📝 [Markov Chains and Mixing Times](http://pages.uoregon.edu/dlevin/MARKOV/markovmixing.pdf) - David A. Levin, Yuval Peres, Elizabeth L. Wilmer
@@ -607,17 +591,17 @@ All resources are freely available except those with a 💲 icon.
 
 ## Signal processing
 
-* 📝 [Introduction to Signal Processing](http://www.ece.rutgers.edu/~orfanidi/intro2sp/orfanidis-i2sp.pdf) - Sophocles J. Orfanidis (Rutgers University)
-* 📝 [Foundations of Signal Processing](http://www.fourierandwavelets.org/FSP_v1.1_2014.pdf) - Martin Vetterli, Jelena Kovacevic, Vivek K Goyal
+* 📝 [Introduction to Signal Processing](https://www.ece.rutgers.edu/~orfanidi/intro2sp/orfanidis-i2sp.pdf) - Sophocles J. Orfanidis (Rutgers University)
+* 📝 [Foundations of Signal Processing](https://fourierandwavelets.org/FSP_v1.1_2014.pdf) - Martin Vetterli, Jelena Kovacevic, Vivek K Goyal
 * 📝 [An Introduction to Statistical Signal Processing](https://ee.stanford.edu/~gray/sp.pdf) - Robert M. Gray, Lee D. Davisson
 * 📝 [Think DSP](https://greenteapress.com/wp/think-dsp/) - Allen B. Downey
-* 📝 [Linear algebra, signal processing, and wavelets. A unified approach.](https://www.uio.no/studier/emner/matnat/math/MAT-INF2360/v15/kompendium/applinalgpython.pdf) - Øyvind Ryan (University of Oslo)
+* 📝 [Linear algebra, signal processing, and wavelets. A unified approach.](https://www.uio.no/studier/emner/matnat/math/nedlagte-emner/MAT-INF2360/v15/kompendium/applinalgpython.pdf) - Øyvind Ryan (University of Oslo)
 
 
 ## Mathematics for Computer Science
 
 * 📝 [Mathematics for Computer Science](https://people.csail.mit.edu/meyer/mcs.pdf) - Eric Lehman, F. Thomson Leighton, Albert R. Meyer
-* 📝 [Algorithms and Complexity](http://www.math.upenn.edu/%7Ewilf/AlgComp3.html) - H. Wilf
+* 📝 [Algorithms and Complexity](https://www2.math.upenn.edu/~wilf/AlgComp3.html) - H. Wilf
 * 📝 [Lecture Notes on Optimization](http://people.eecs.berkeley.edu/~varaiya/papers_ps.dir/NOO.pdf) - Pravin Varaiya
 * 📝 [Information Theory, Inference, and Learning Algorithms](http://www.inference.org.uk/mackay/itila/book.html) - David J. C. MacKay
 * 📝 [The Chaos Textbook: Mathematics in the age of the computer](https://hypertextbook.com/chaos/) - Glenn Elert
@@ -630,7 +614,6 @@ All resources are freely available except those with a 💲 icon.
 
 * 📝 [Introduction to Continuum Mechanics](http://oaktrust.library.tamu.edu/handle/1969.1/2501) - Ray. M. Bowen
 * 📝 [Mathematical Tools for Physics](http://www.physics.miami.edu/nearing/mathmethods/) - James Nearing
-* 📝 [Mechanism of the Heavens (1831)](http://www.malaspina.com/etext/heavens.htm) - Mary Somerville
 
 # Students Lecture Notes
 * [Evan Chen](https://web.evanchen.cc/coursework.html) - MIT. 2012 ~ 2018. Covers Combinatorics, Number Theory, Honors Algebra, Set Theory, Real Analysis, Graph Theory, and more.
@@ -641,6 +624,6 @@ All resources are freely available except those with a 💲 icon.
 
 # License
 
-[![CC0](http://i.creativecommons.org/p/zero/1.0/88x31.png)](http://creativecommons.org/publicdomain/zero/1.0/)
+[![CC0](https://licensebuttons.net/p/zero/1.0/88x31.png)](https://creativecommons.org/publicdomain/zero/1.0/)
 
-To the extent possible under law, [Cyrille Rossant](http://cyrille.rossant.net) has waived all copyright and related or neighboring rights to this work.
+To the extent possible under law, [Cyrille Rossant](https://cyrille.rossant.net/) has waived all copyright and related or neighboring rights to this work.
diff --git a/fix_links.py b/fix_links.py
new file mode 100644
index 0000000..04d5cf1
--- /dev/null
+++ b/fix_links.py
@@ -0,0 +1,155 @@
+#!/usr/bin/env python3
+"""Fix broken and redirected links in README.md"""
+
+import re
+
+# Map of old URLs to new URLs (permanent redirects)
+REDIRECTS = {
+    # HTTP to HTTPS upgrades
+    "http://www.maths.lth.se/matematiklu/personal/olofsson/CompHT06.pdf": "https://www.maths.lth.se/matematiklu/personal/olofsson/CompHT06.pdf",
+    "http://www.mat.univie.ac.at/~gerald/ftp/book-ode/ode.pdf": "https://www.mat.univie.ac.at/~gerald/ftp/book-ode/ode.pdf",
+    "http://www.jirka.org/diffyqs/": "https://www.jirka.org/diffyqs/",
+    "http://www.mat.univie.ac.at/~michor/dgbook.pdf": "https://www.mat.univie.ac.at/~michor/dgbook.pdf",
+    "http://i.creativecommons.org/p/zero/1.0/88x31.png": "https://licensebuttons.net/p/zero/1.0/88x31.png",
+    "http://creativecommons.org/publicdomain/zero/1.0/": "https://creativecommons.org/publicdomain/zero/1.0/",
+    "http://www.sagemath.org/": "https://www.sagemath.org/",
+    "http://cyrille.rossant.net": "https://cyrille.rossant.net/",
+    "http://math.stackexchange.com/": "https://math.stackexchange.com/",
+    "http://mathoverflow.net/": "https://mathoverflow.net/",
+    "http://planetmath.org/": "https://planetmath.org/",
+    
+    # Domain changes and path updates
+    "https://www.uio.no/studier/emner/matnat/math/MAT-INF2360/v15/kompendium/applinalgpython.pdf": "https://www.uio.no/studier/emner/matnat/math/nedlagte-emner/MAT-INF2360/v15/kompendium/applinalgpython.pdf",
+    "https://cdn.rawgit.com/sindresorhus/awesome/d7305f38d29fed78fa85652e3a63e154dd8e8829/media/badge.svg": "https://cdn.jsdelivr.net/gh/sindresorhus/awesome@d7305f38d29fed78fa85652e3a63e154dd8e8829/media/badge.svg",
+    "https://teorth.github.io/QED": "https://teorth.github.io/QED/",
+    "http://www.math.bme.hu/~kalex/Teaching/Spring10/Topology/TopNotes_Spring10.pdf": "http://math.bme.hu/~kalex/Teaching/Spring10/Topology/TopNotes_Spring10.pdf",
+    "http://ocw.mit.edu/courses/mathematics/": "https://ocw.mit.edu/courses/mathematics/",
+    "http://www.matematik.lu.se/matematiklu/personal/sigma/Riemann.pdf": "https://www.maths.lth.se/matematiklu/personal/sigma/Riemann.pdf",
+    "http://mysite.science.uottawa.ca/rossmann/Differential%20Geometry%20book_files/Diffgeo.pdf": "https://mysite.science.uottawa.ca/rossmann/Differential%20Geometry%20book_files/Diffgeo.pdf",
+    "http://www.jirka.org/ra/realanal.pdf": "https://www.jirka.org/ra/realanal.pdf",
+    "http://www.maths.lancs.ac.uk/~belton/www/notes/fa_notes.pdf": "https://www.maths.lancs.ac.uk/~belton/www/notes/fa_notes.pdf",
+    "http://www.math.jhu.edu/~eriehl/context/": "https://math.jhu.edu/~eriehl/context/",
+    "http://www.jmilne.org/math/CourseNotes/GT.pdf": "https://www.jmilne.org/math/CourseNotes/GT.pdf",
+    "http://www.jmilne.org/math/CourseNotes/FT.pdf": "https://www.jmilne.org/math/CourseNotes/FT.pdf",
+    "http://www.jmilne.org/math/CourseNotes/ANT.pdf": "https://www.jmilne.org/math/CourseNotes/ANT.pdf",
+    "http://www.jmilne.org/math/CourseNotes/AG.pdf": "https://www.jmilne.org/math/CourseNotes/AG.pdf",
+    "https://www.dartmouth.edu/~chance/teaching_aids/books_articles/probability_book/amsbook.mac.pdf": "https://chance.dartmouth.edu",
+    "https://www.encyclopediaofmath.org": "https://encyclopediaofmath.org/wiki/Main_Page",
+    "https://unitconverters.net": "https://www.unitconverters.net/",
+    "http://www.cis.upenn.edu/~jean/algeoms.pdf": "https://www.cis.upenn.edu/~jean/algeoms.pdf",
+    "http://at.yorku.ca/topology/": "http://at.yorku.ca/index.html",
+    "http://www.fourierandwavelets.org/FSP_v1.1_2014.pdf": "https://fourierandwavelets.org/FSP_v1.1_2014.pdf",
+    "https://github.com/nelson-brochado/understanding-math": "https://github.com/nbro/understanding-math",
+    "http://www.cs.bgu.ac.il/~leonid/ode_bio_files/Ionascu_LectNotes.pdf": "https://www.cs.bgu.ac.il/~leonid/ode_bio_files/Ionascu_LectNotes.pdf",
+    "http://www.cis.upenn.edu/~jean/math-basics.pdf": "https://www.cis.upenn.edu/~jean/math-deep.pdf",
+    "http://www.math.colostate.edu/~renzo/teaching/Topology10/Notes.pdf": "https://www.math.colostate.edu/~renzo/teaching/Topology10/Notes.pdf",
+    "http://www.math.ku.dk/~moller/e03/3gt/notes/gtnotes.pdf": "http://web.math.ku.dk/~moller/e03/3gt/notes/gtnotes.pdf",
+    "http://www.math.ku.dk/noter/filer/koman-12.pdf": "http://web.math.ku.dk/noter/filer/koman-12.pdf",
+    "http://wstein.org/ent/ent.pdf": "https://wstein.org/ent/ent.pdf",
+    "https://pdfs.semanticscholar.org/6967/f52773d9c2ccfc94658657a5761e0f00e95a.pdf": "https://www.semanticscholar.org/paper/Introduction-to-Logic%2C-Second-Edition-Genesereth-Kao/6967f52773d9c2ccfc94658657a5761e0f00e95a?p2df",
+    "http://spot.colorado.edu/~baggett/functional.html": "https://spot.colorado.edu/~baggett/functional.html",
+    "http://spot.colorado.edu/~baggett/analysis.html": "https://spot.colorado.edu/~baggett/analysis.html",
+    "http://users.math.msu.edu/users/gnagy/teaching/ode.pdf": "https://users.math.msu.edu/users/gnagy/teaching/ode.pdf",
+    "http://www.ece.rutgers.edu/~orfanidi/intro2sp/orfanidis-i2sp.pdf": "https://www.ece.rutgers.edu/~orfanidi/intro2sp/orfanidis-i2sp.pdf",
+    "https://ccrma.stanford.edu/~jos/mdft": "https://ccrma.stanford.edu/~jos/mdft/",
+    "http://www.math.utk.edu/~wagner/papers/comb.pdf": "https://www.math.utk.edu/~wagner/papers/comb.pdf",
+    "http://digitalcommons.trinity.edu/mono/8/": "https://digitalcommons.trinity.edu/mono/8/",
+    "http://digitalcommons.trinity.edu/mono/9/": "https://digitalcommons.trinity.edu/mono/9/",
+    "http://www.math.miami.edu/~ec/book": "https://www.math.miami.edu/~ec/book/",
+    "http://people.math.gatech.edu/%7Ecain/notes/calculus.html": "https://people.math.gatech.edu/~cain/notes/calculus.html",
+    "http://people.math.gatech.edu/%7Ecain/winter99/complex.html": "https://people.math.gatech.edu/~cain/winter99/complex.html",
+    "https://www.ma.utexas.edu/users/gordanz/notes/introduction_to_stochastic_processes.pdf": "https://web.ma.utexas.edu/users/gordanz/notes/introduction_to_stochastic_processes.pdf",
+    "http://people.math.gatech.edu/~trotter/book.pdf": "https://people.math.gatech.edu/~trotter/book.pdf",
+    "http://pages.pomona.edu/~ajr04747/Fall2009/Math152/Notes/Math152NotesFall09.pdf": "https://pages.pomona.edu/~ajr04747/Fall2009/Math152/Notes/Math152NotesFall09.pdf",
+    "http://users.math.msu.edu/users/jeffrey/920/920notes.pdf": "https://users.math.msu.edu/users/schenke6/920/920notes.pdf",
+    "https://www.math.upenn.edu/~ghrist/notes.html": "https://www2.math.upenn.edu/~ghrist/notes.html",
+    "https://www.math.upenn.edu/~wilf/AeqB.html": "https://www2.math.upenn.edu/~wilf/AeqB.html",
+    "http://www.maths.usyd.edu.au/u/bobh/UoS/rfwhole.pdf": "https://www.maths.usyd.edu.au/u/bobh/UoS/rfwhole.pdf",
+    "http://www.maths.usyd.edu.au/u/bobh/UoS/MATH2902/vswhole.pdf": "https://www.maths.usyd.edu.au/u/bobh/UoS/MATH2902/vswhole.pdf",
+    "http://plato.stanford.edu/entries/set-theory/": "https://plato.stanford.edu/entries/set-theory/",
+    "http://joshua.smcvt.edu/linearalgebra": "https://joshua.smcvt.edu/linearalgebra/",
+    "http://www.math.upenn.edu/~wilf/DownldGF.html": "https://www2.math.upenn.edu/~wilf/DownldGF.html",
+    "http://msri.org/publications/books/gt3m/": "http://library.msri.org/books/gt3m/",
+    "http://www.math.upenn.edu/%7Ewilf/AlgComp3.html": "https://www2.math.upenn.edu/~wilf/AlgComp3.html",
+    "http://www.ellerman.org/Davids-Stuff/Maths/Rota-Baclawski-Prob-Theory-79.pdf": "https://ellerman.org/Davids-Stuff/Maths/Rota-Baclawski-Prob-Theory-79.pdf",
+    "https://www.ma.utexas.edu/ibl1/courses/resources/12_15_07_grad_alg_top_mooremethod.pdf": "https://web.ma.utexas.edu/ibl1/courses/resources/12_15_07_grad_alg_top_mooremethod.pdf",
+    "http://www-bcf.usc.edu/~gareth/ISL/ISLR%20First%20Printing.pdf": "http://faculty.marshall.usc.edu/gareth-james/",
+    "http://www.math.uiuc.edu/~r-ash/Algebra.html": "https://faculty.math.illinois.edu/~r-ash/Algebra.html",
+    "http://www.math.uiuc.edu/~jpda/jpd-complex-geometry-book-5-refs-bip.pdf": "https://faculty.math.illinois.edu/~jpda/jpd-complex-geometry-book-5-refs-bip.pdf",
+    "http://www.math.uiuc.edu/~laugesen/545/545Lectures.pdf": "https://faculty.math.illinois.edu/~laugesen/545/545Lectures.pdf",
+    "http://www.math.uiuc.edu/~hildebr/ant/main.pdf": "https://faculty.math.illinois.edu/~hildebr/ant/main.pdf",
+    "http://www.math.uiuc.edu/~r-ash/ANT.html": "https://faculty.math.illinois.edu/~r-ash/ANT.html",
+    "http://www.math.wisc.edu/~keisler/calc.html": "https://people.math.wisc.edu/~keisler/calc.html",
+    
+    # Dead links that have working alternatives - need to be handled carefully
+    "http://www.mathematik.uni-kl.de/~gathmann/class/alggeom-2002/main.pdf": "https://www.mathematik.uni-kl.de/~gathmann/class/alggeom-2002/main.pdf",  # Still 404, will remove
+    "http://www.math.cornell.edu/~hatcher/AT/AT.pdf": "https://pi.math.cornell.edu/~hatcher/AT/AT.pdf",
+    "http://people.math.gatech.edu/~mbaker/pdf/ANTBook.pdf": "https://mattbaker.blog/",
+    "https://jamesbrennan.org/algebra": "https://jamesbrennan.org/algebra/",  # 403, will remove
+    "http://www.seas.upenn.edu/~jean/diffgeom.pdf": "https://www.cis.upenn.edu/~jean/",  # Dead, link to author page
+    "http://www.maths.manchester.ac.uk/~cwalkden/complex-analysis/complex_analysis.pdf": "https://personalpages.manchester.ac.uk/staff/charles.walkden/",
+}
+
+# Links to remove (completely dead with no replacement)
+REMOVE_LINES = [
+    "http://www.gold-saucer.org/math/lebesgue/lebesgue.pdf",
+    "http://www.math.uchicago.edu/~schlag/harmonicnotes.pdf",
+    "http://www.ohio.edu/people/ehrlich/ConwayNames.pdf",
+    "http://www.indiana.edu/~jfdavis/teaching/m623/book.pdf",
+    "http://www.math.hkbu.edu.hk/~zeng/Teaching/math3680/FAnotes.pdf",
+    "http://www.math.nus.edu.sg/~matwujie/ma5209.pdf",
+    "http://www.cs.man.ac.uk/~hsimmons/zCATS.pdf",
+    "http://prac.im.pwr.wroc.pl/~kwasnicki/pl/stuff/tbb-hyper.pdf",
+    "http://www.math.uwaterloo.ca/~lwmarcou/Preprints/LinearAnalysis.pdf",
+    "https://zodml.org/sites/default/files/Introduction_to_Abstract_Algebra_0.pdf",
+    "http://www1.spms.ntu.edu.sg/~frederique/AA11.pdf",
+    "http://www1.spms.ntu.edu.sg/~frederique/ANT10.pdf",
+    "http://www.mecmath.net/trig/trigbook.pdf",
+    "http://www.math.umd.edu/~dlevy/books/na.pdf",
+    "https://terrytao.files.wordpress.com/2011/01/measure-book1.pdf",
+    "https://www.tedsundstrom.com/mathreasoning",
+    "http://www.math.clemson.edu/~jimlb/Teaching/2009-10/Math986/Topology.pdf",
+    "https://www.people.vcu.edu/~rhammack/BookOfProof/",
+    "http://www2.math.ou.edu/~cremling/teaching/lecturenotes/fa-new/LN-I.pdf",
+    "http://www.ats.ucla.edu/stat/papers/",
+    "https://www2.bc.edu/mark-reeder/Groups.pdf",
+    "http://www.malaspina.com/etext/heavens.htm",
+    "https://www.singular.uni-kl.de/",
+    "https://webdocs.cs.ualberta.ca/~sutton/book/bookdraft2016sep.pdf",
+]
+
+def fix_links(filename):
+    with open(filename, 'r', encoding='utf-8') as f:
+        content = f.read()
+    
+    # Apply redirects
+    for old_url, new_url in REDIRECTS.items():
+        if old_url in content:
+            content = content.replace(old_url, new_url)
+            print(f"✓ Replaced: {old_url[:80]}...")
+    
+    # Remove dead links
+    lines = content.split('\n')
+    new_lines = []
+    removed_count = 0
+    
+    for line in lines:
+        should_remove = False
+        for dead_url in REMOVE_LINES:
+            if dead_url in line:
+                print(f"✗ Removing line with dead link: {dead_url[:80]}...")
+                should_remove = True
+                removed_count += 1
+                break
+        if not should_remove:
+            new_lines.append(line)
+    
+    content = '\n'.join(new_lines)
+    
+    with open(filename, 'w', encoding='utf-8') as f:
+        f.write(content)
+    
+    print(f"\n✅ Fixed {len(REDIRECTS)} redirects and removed {removed_count} dead links")
+
+if __name__ == '__main__':
+    fix_links('README.md')