M. Califf, and R. Mooney. Proceedings of the sixteenth national conference on Artificial intelligence and the eleventh Innovative applications of artificial intelligence conference innovative applications of artificial intelligence, page 328--334. Menlo Park, CA, USA, American Association for Artificial Intelligence, (1999)
F. Ciravegna. Proceedings of the 17th international joint conference on Artificial intelligence - Volume 2, page 1251--1256. San Francisco, CA, USA, Morgan Kaufmann Publishers Inc., (2001)