L. Backstrom, J. Kleinberg, R. Kumar, and J. Novak. WWW '08: Proceeding of the 17th international conference on World Wide Web, page 357--366. New York, NY, USA, ACM, (2008)
D. Beeferman, and A. Berger. KDD '00: Proceedings of the sixth ACM SIGKDD international conference on Knowledge discovery and data mining, page 407--416. New York, NY, USA, ACM, (2000)
B. Jansen, D. Booth, and A. Spink. WWW '07: Proceedings of the 16th international conference on World Wide Web, page 1149--1150. New York, NY, USA, ACM, (2007)