G. Feng, T. Liu, Y. Wang, Y. Bao, Z. Ma, X. Zhang, and W. Ma. Proceedings of the 29th annual international ACM SIGIR conference on Research and development in information retrieval - SIGIR \textquotesingle06, ACM Press, (2006)
D. Liu, X. Hua, L. Yang, M. Wang, and H. Zhang. Proceedings of the 18th international conference on World wide web, page 351--360. New York, NY, USA, ACM, (2009)
P. Yu, X. Li, and B. Liu. Proceedings of the 13th international World Wide Web conference on Alternate track papers & posters, page 448--449. New York, NY, USA, ACM, (2004)
Y. Liu, B. Gao, T. Liu, Y. Zhang, Z. Ma, S. He, and H. Li. Proceedings of the 31st annual international ACM SIGIR conference on Research and development in information retrieval, page 451--458. New York, NY, USA, ACM, (2008)