Merge pull request #1364 from sengopal/master

Updated the broken link for "Mathematics for computer science" with the available one

free-programming-books.md

@@ -391,7 +391,7 @@ Original Source: [Free Programming books](http://stackoverflow.com/revisions/392
 
 #### Mathematics For Computer Science
 
-* [Mathematics for Computer Science (November 2013 Version)](https://www.cs.princeton.edu/courses/archive/fall13/cos340/LLM.pdf) (PDF) - Eric Lehman
+* [Mathematics for Computer Science (January 2012 Version)](https://www.seas.harvard.edu/courses/cs20/MIT6_042Notes.pdf) (PDF) - Eric Lehman
 * [Discrete Structures for Computer Science: Counting, Recursion, and Probability](http://cglab.ca/~michiel/DiscreteStructures/) - Michiel Smid