1. Object Management Group, OMG Unified Modeling Language Specification, Version 1.3, June 1999, http://www.rational.com .
2. R. B. France, A. Evans, K. Lano, and B. Rumpe, Developing the UML as a Formal Modeling Notation, Computer Standards and Interfaces, No 19, pp. 325–334, 1998.
3. M. Bickford and D. Guaspari, Odyssey Research Associates Report No. 10, 1998.
4. A. Hamie, “A Formal Semantics for Checking and Analysing UML Models”, in Proceedings of the OOPSLA’98 Workshop on Formalizing UML. Why? How?, edited by L. Andrade, A. Moreira, A. Deshpande, and S. Kent, 1998.
5. A. Hamie, J. Howse, and S. Kent, “Interpreting the Object Constraint Language”, in Proceedings of Asia Pacific Conference in Software Engineering, IEEE Press, 1998.