Merge pull request #1297 from gortok/so-cc

Adding CC-By-SA requirements for attribution

free-programming-books.md

@@ -1,3 +1,8 @@
+Original Contribution by [George Stocker](http://stackoverflow.com/users/16587/george-stocker) on [Stack Overflow](http://stackoverflow.com)
+
+Original Source: [Free Programming books](http://stackoverflow.com/revisions/392926/175)
+
+
 ### Index
 * [Ada](#ada)
 * [Agda](#agda)