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)
B. Richards, and R. Mooney. Proceedings of the 10th National Conference on Artificial Intelligence (AAAI-92), page 174--185. San Jose, CA, USA, (July 1992)