P. Melville, R. Mooney, and R. Nagarajan. Eighteenth National Conference on Artificial Intelligence, page 187--192. Menlo Park, CA, USA, American Association for Artificial Intelligence, (2002)
R. Torres, S. McNee, M. Abel, J. Konstan, and J. Riedl. Proceedings of the 4th ACM/IEEE-CS Joint Conference on Digital Libraries, page 228--236. New York, NY, USA, ACM, (2004)