Ruth Breu Ursula Hinkel Christoph Hofmann Cornel Klein Barbara Paech Bernhard Rumpe Veronika Thurner Towards a Formalization of the Unified Modeling Language. 344-366 http://link.springer.de/link/service/series/0558/bibs/1241/12410344.htm 1997 ECOOP db/conf/ecoop/ecoop97.html#BreuHHKPRT97