U. Fayyad, G. Piatetsky-Shapiro, and P. Smyth. Advances in knowledge discovery and data mining, American Association for Artificial Intelligence, Menlo Park, CA, USA, (1996)
R. Agrawal, and R. Srikant. VLDB '94: Proceedings of the 20th International Conference on Very Large Data Bases, page 487--499. San Francisco, CA, USA, Morgan Kaufmann Publishers Inc., (1994)