M. Hearst. Proceedings of the 37th annual meeting of the Association for Computational
Linguistics on Computational Linguistics, page 3--10. Morristown, NJ, USA, Association for Computational Linguistics, (1999)
Y. Yang, and J. Pedersen. Proceedings of the Fourteenth International Conference on Machine Learning, page 412--420. San Francisco, CA, USA, Morgan Kaufmann Publishers Inc., (1997)