D. Zhou, J. Bian, S. Zheng, H. Zha, and C. Giles. WWW '08: Proceeding of the 17th international conference on World Wide Web, page 715--724. New York, NY, USA, ACM, (2008)
G. Kazai, and N. Milic-Frayling. CIKM '08: Proceeding of the 17th ACM conference on Information and knowledge mining, page 1503--1504. New York, NY, USA, ACM, (2008)
J. Zhang, and M. Ackerman. GROUP '05: Proceedings of the 2005 international ACM SIGGROUP conference on Supporting group work, page 71--80. New York, NY, USA, ACM, (2005)