M. Fisher, and C. Ghidini. Proceedings of the Sixteenth International Joint Conference on Artificial Intelligence (IJCAI'99), page 200--205. Stockholm, Morgan Kaufmann Publ., Inc, (31 July -- 6 August 1999)
J. Delgrande, J. Lang, and T. Schaub. IJCAI'07: Proceedings of the 20th international joint conference on Artifical intelligence, page 2462--2467. San Francisco, CA, USA, Morgan Kaufmann Publishers Inc., (2007)