Adding reference to the uml 2.0 reference

bac2/pgl/usecase/references.bib

@@ -0,0 +1,9 @@
+@BOOK{Pilone2006-fn,
+  title     = "{UML} 2.0 Pocket Reference",
+  author    = "Pilone, Dan",
+  publisher = "O'Reilly Media",
+  month     =  mar,
+  year      =  2006,
+  address   = "Sebastopol, CA",
+  language  = "en"
+}