P. Melville, R. Mooney, и R. Nagarajan. Eighteenth National Conference on Artificial Intelligence, стр. 187--192. Menlo Park, CA, USA, American Association for Artificial Intelligence, (2002)
K. Lang. Proceedings of the 12th International Conference on Machine Learning, стр. 331--339. Morgan Kaufmann publishers Inc.: San Mateo, CA, USA, (1995)