http://www.extremeprogramming.org/rules/userstories.html : This is the main website for eXtreme Programming (XP), an approach to software development currently popular among practitioners. User stories are commonly used among XP practitioners to capture requirements.
The Unified Modeling Language User Guide, 2e, G Booch, J Rumbaugh, and I Jacobson
[uml-distilled] UML distilled by Martin Fowler
Mercurial: The Definitive Guide by Bryan O'Sullivan retrieved on 2012/07/11