B. Henderson-Sellers, D. Zowghi, T. Klemola, and S. Parasuram. Object-Oriented. Information Systems, 8th International Conference, OOIS 2002, volume 2425 of Lecture Notes in Computer Science, page 409-421. Springer, (2002)
M. Ehrig, A. Koschmider, and A. Oberweis. APCCM '07: Proceedings of the fourth Asia-Pacific conference on Comceptual modelling, page 71--80. Darlinghurst, Australia, Australia, Australian Computer Society, Inc., (2007)
G. Kaiser, D. Perry, and W. Schell. Computer Software and Applications Conference, 1989. COMPSAC 89., Proceedings of the 13th Annual International, page 552-558. (1989)