P. Schonhofen. WI '06: Proceedings of the 2006 IEEE/WIC/ACM International Conference on Web Intelligence, page 456--462. Washington, DC, USA, IEEE Computer Society, (2006)
J. Hu, G. Wang, F. Lochovsky, J. tao Sun, and Z. Chen. WWW '09: Proceedings of the 18th international conference on World wide web, page 471--480. New York, NY, USA, ACM, (2009)