Merge pull request #1354 from MauriceWhite/patch-1

Update free-programming-books.md

free-programming-books.md

@@ -372,6 +372,7 @@ Original Source: [Free Programming books](http://stackoverflow.com/revisions/392
 * [Elementary Differential Equations](http://ramanujan.math.trinity.edu/wtrench/texts/TRENCH_DIFF_EQNS_I.PDF) - William F. Trench
 * [Essentials of Metaheuristics](http://cs.gmu.edu/~sean/book/metaheuristics/) by Sean Luke
 * [Introduction to Probability](http://www.dartmouth.edu/~chance/teaching_aids/books_articles/probability_book/book.html) - Charles M. Grinstead and J. Laurie Snell
+* [Introduction to Probability and Statistics Spring 2014](http://ocw.mit.edu/courses/mathematics/18-05-introduction-to-probability-and-statistics-spring-2014/)
 * [Introduction to Statistical Thought](http://www.math.umass.edu/~lavine/Book/book.html) - Michael Lavine
 * [Linear Algebra](https://www.math.ucdavis.edu/~linear/linear-guest.pdf)
 * [Linear Algebra: An Introduction to Mathematical Discourse](http://en.wikibooks.org/wiki/Linear_Algebra) - Jim Hefferon