D. Shen, Z. Chen, Q. Yang, H. Zeng, B. Zhang, Y. Lu, and W. Ma. SIGIR '04: Proceedings of the 27th annual international conference on Research and development in information retrieval, page 242--249. New York, NY, USA, ACM Press, (2004)
G. Qiu, K. Liu, J. Bu, C. Chen, and Z. Kang. SIGIR '07: Proceedings of the 30th annual international ACM SIGIR conference on Research and development in information retrieval, page 697--698. New York, NY, USA, ACM, (2007)
S. Dumais, and H. Chen. Proceedings of the 23rd annual international ACM SIGIR conference on Research and development in information retrieval, page 256--263. Athens, Greece, ACM Press, (July 2000)