H. Ma, H. Yang, I. King, and M. Lyu. CIKM '08: Proceeding of the 17th ACM conference on Information and knowledge mining, page 709--718. New York, NY, USA, ACM, (2008)
G. Xue, H. Zeng, Z. Chen, Y. Yu, W. Ma, W. Xi, and W. Fan. CIKM '04: Proceedings of the thirteenth ACM international conference on Information and knowledge management, page 118--126. New York, NY, USA, ACM, (2004)