B. Sarwar, G. Karypis, J. Konstan, and J. Riedl. Proceedings of the 2nd ACM Conference on Electronic Commerce, page 158--167. New York, NY, USA, ACM, (2000)
T. Joachims, L. Granka, B. Pan, H. Hembrooke, and G. Gay. Proceedings of the 28th Annual International Conference on Research and Development in Information Retrieval, page 154--161. New York, NY, USA, ACM, (2005)
I. Niemelä, P. Simons, and T. Soininen. Proceedings of the 5th International Conference on Logic Programming and Nonmonotonic Reasoning, page 317--331. London, UK, Springer-Verlag, (1999)
M. Stumpner, A. Haselbock, and G. Friedrich. Proceedings of the 10th Conference on Artificial Intelligence for Applications, page 373-380. San Antonia, TX, USA, (1994)
R. Cunis, A. Günter, I. Syska, H. Peters, and H. Bode. Proceedings of the 2nd International Conference on Industrial and Engineering applications of artificial intelligence and expert systems - Volume 2, page 866--874. New York, NY, USA, ACM, (1989)
G. Greco, S. Greco, and E. Zumpano. Proceedings of the 17th International Conference on Logic Programming, page 348--364. London, UK, UK, Springer-Verlag, (2001)
M. Arenas, L. Bertossi, and J. Chomicki. Proceedings of the 18th Symposium on Principles of Database Systems, page 68--79. New York, NY, USA, ACM, (1999)
M. Casanova, R. Fagin, and C. Papadimitriou. Proceedings of the Symposium on Principles of Database Systems, page 171--176. New York, NY, USA, ACM, (1982)
A. Cal\`ı, D. Lembo, and R. Rosati. Proceedings of the Twenty-Second Symposium on Principles of Database Systems, page 260--271. New York, NY, USA, ACM, (2003)
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)