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)
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)
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)