Merge pull request #84 from joao29a/master

Professional Assembly Language book and Racket guide

free-programming-books.md

@@ -240,6 +240,7 @@
 ###Assembly Language
 
 * [Paul Carter's Tutorial on x86 Assembly](http://drpaulcarter.com/pcasm/)
+* [Professional Assembly Language](http://blog.hit.edu.cn/jsx/upload/AT%EF%BC%86TAssemblyLanguage.pdf)
 * [Programming from the Ground Up](http://download.savannah.gnu.org/releases/pgubook/ProgrammingGroundUp-1-0-booksize.pdf) (PDF)
 * [Software optimization resources by Agner Fog](http://www.agner.org/optimize/)
 
@@ -641,6 +642,7 @@
 
 ###Racket
 * [Programming Languages: Application and Interpretation](http://cs.brown.edu/courses/cs173/2012/book/index.html)
+* [The Racket Guide](http://docs.racket-lang.org/guide/index.html)
 
 
 ###Ruby