B. Liu, W. Hsu, K. Wang, and S. Chen. Proceedings of the 3nd Pacific-Asia international conference on research
and development in Knowledge Discovery and Data mining (PAKDD'99), page 380--389. Springer-Verlag, (April 1999)
B. Liu, W. Hsu, and Y. Ma. Proceedings of the 4th international conference on Knowledge Discovery
and Data mining (KDD'98), page 80--86. AAAI Press, (August 1998)