D. Kalibatiene, and O. Vasilecas. CompSysTech '08: Proceedings of the 9th International Conference
on Computer Systems and Technologies and Workshop for PhD Students
in Computing, page V.1--1. New York, NY, USA, ACM, (2008)
G. Guizzardi, H. Herre, and G. Wagner. ER '02: Proceedings of the 21st International Conference on Conceptual
Modeling, page 65--78. London, UK, Springer-Verlag, (2002)