Here are a couple of references I use sometimes http://www.holub.com/goodies/uml/index.html http://www-306.ibm.com/software/rational/uml/ http://www.omg.org/technology/documents/formal/uml.htm http://www.foruse.com/publications/bibliographies/usecases.htm I find that if I'm having a block, I usually need to re-examine my understanding of the domain and/or re-examine the use cases. Hth -chris