Merge pull request #1584 from borgified/master

fixes pull #1569

free-programming-books.md

@@ -735,6 +735,7 @@ Original Source: [Free Programming books](http://stackoverflow.com/revisions/392
 * [Advanced Bash-Scripting Guide](http://tldp.org/LDP/abs/html/)
 * [Bash Guide for Beginners](http://www.tldp.org/LDP/Bash-Beginners-Guide/html/) by Machtelt Garrels
 * [BASH Programming- Mike G mikkey](http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html)
+* [Bash Reference Manual](http://www.gnu.org/software/bash/manual/bashref.html)
 * [Conquering the Command Line](http://conqueringthecommandline.com/book/frontmatter) - Mark Bates
 * [Getting Started with BASH](http://www.hypexr.org/bash_tutorial.php)
 * [Google Shell Style Guide](http://google-styleguide.googlecode.com/svn/trunk/shell.xml)