1. Object Management Group: OMG object constraint language (OCL). Technical Report formal/2012-01-01, Object Management Group, Inc. (2012)
2. Lecture Notes in Computer Science;L. Mandel,1999
3. Lecture Notes in Computer Science;H. Balsters,2003
4. Queralt, A., Teniente, E.: Verification and validation of UML conceptual schemas with OCL constraints. ACM Trans. Softw. Eng. Methodol. 21(2), 13 (2012)
5. Clavel, M., Egea, M., de Dios, M.A.G.: Checking unsatisfiability for OCL constraints. In: Proceedings of the Workshop The Pragmatics of OCL and Other Textual Specification Languages, vol. 24. ECEASST (2009)