B. Zhang, H. Li, Y. Liu, L. Ji, W. Xi, W. Fan, Z. Chen, and W. Ma. SIGIR '05: Proceedings of the 28th annual international ACM SIGIR conference on Research and development in information retrieval, page 504--511. New York, NY, USA, ACM, (2005)
J. Sun, H. Zeng, H. Liu, Y. Lu, and Z. Chen. WWW '05: Proceedings of the 14th international conference on World Wide Web, page 382--390. New York, NY, USA, ACM Press, (May 2005)