G. Murphy, and D. Notkin. Proceedings of SIGSOFT 1995, Third ACM SIGSOFT Symposium on the Foundations of Software Engineering, page 116--127. ACM Press, (1995)
I. Borne, F. e Abreu, W. Meuter, and G. Galal. ECOOP 1998 Workshop Reader, volume 1543 of Lecture Notes in Computer Science, page 44-71. Springer-Verlag, (1998)