Y. Song, Z. Zhuang, H. Li, Q. Zhao, J. Li, W. Lee, and C. Giles. Proceedings of the 31st Annual International ACM SIGIR Conference on Research and Development in Information Retrieval, page 515--522. New York, NY, USA, ACM, (2008)
H. Yang, S. Parthasarathy, and S. Mehta. KDD '05: Proceeding of the eleventh ACM SIGKDD international conference on Knowledge discovery in data mining, page 716--721. New York, NY, USA, ACM Press, (2005)