F. Ciravegna. Proceedings of the 17th international joint conference on Artificial intelligence - Volume 2, стр. 1251--1256. San Francisco, CA, USA, Morgan Kaufmann Publishers Inc., (2001)
M. Califf, и 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, стр. 328--334. Menlo Park, CA, USA, American Association for Artificial Intelligence, (1999)