A. Evans, R. France, K. Lano, and B. Rumpe. &\#171;UML&\#187; '98: Selected papers from the First International Workshop on The Unified Modeling Language &\#171;UML&\#187;'98, page 336--348. London, UK, Springer-Verlag, (1999)
A. Cal&\#236;, D. Calvanese, G. Giacomo, and M. Lenzerini. ISMIS '02: Proceedings of the 13th International Symposium on Foundations of Intelligent Systems, page 503--513. London, UK, Springer-Verlag, (2002)
A. Evans. WIFT '98: Proceedings of the Second IEEE Workshop on Industrial Strength Formal Specification Techniques, page 102. Washington, DC, USA, IEEE Computer Society, (1998)
R. Straeten, T. Mens, J. Simmonds, and V. Jonckers. UML 2003 – The Unified Modeling Language, volume 2863 of Lecture Notes in Computer Science, page 326--340. Springer, (2003)