R. Van Der Straeten, V. Jonckers, and T. Mens. UML 2004 - The Unified Modeling Language, volume 3273 of Lecture Notes in Computer Science, page 305--319. Springer-Verlag, (October 2004)
P. Van Gorp, H. Stenten, T. Mens, and S. Demeyer. UML 2003 - The Unified Modeling Language, volume 2863 of Lecture Notes in Computer Science, page 144--158. Springer-Verlag, (2003)
A. van Deursen, and L. Moonen. Proc. Int'l Conf. eXtreme Programming and Flexible Processes in Software Engineering (XP), page 71--76. (2002)Alghero, Sardinia, Italy.