U. Junker. Proceedings of the 19th National Conference on Artificial Intelligence, page 167--172. Menlo Park, California, AAAI Press / The MIT Press, (2004)
R. Srikant, Q. Vu, and R. Agrawal. Proceedings of the Third International Conference of Knowledge Discovery and Data Mining, page 67--73. Menlo Park, California, AAAI Press, (1997)