R. Bakker, F. Dikker, F. Tempelman, and P. Wogmim. Proceedings of the 13th International Joint Conference on Artifical Intelligence, page 276--281. San Francisco, CA, USA, Morgan Kaufmann Publishers Inc., (1993)
G. Engels, J. Küster, R. Heckel, and L. Groenewegen. ESEC/FSE-9: Proceedings of the 8th European software engineering conference held jointly with 9th ACM SIGSOFT international symposium on Foundations of software engineering, 26, page 186--195. New York, NY, USA, ACM Press, (September 2001)