Y. Yang, and X. Liu. SIGIR '99: Proceedings of the 22nd annual international ACM SIGIR conference on Research and development in information retrieval, page 42--49. New York, NY, USA, ACM Press, (1999)
R. Jäschke, L. Marinho, A. Hotho, L. Schmidt-Thieme, and G. Stumme. Knowledge Discovery in Databases: PKDD 2007, 11th European Conference on Principles and Practice of Knowledge Discovery in Databases, Warsaw, Poland, September 17-21, 2007, Proceedings, volume 4702 of Lecture Notes in Computer Science, page 506-514. Springer, (2007)