B. Piwowarski, G. Dupret, and R. Jones. WSDM '09: Proceedings of the Second ACM International Conference on Web Search and Data Mining, page 162--171. New York, NY, USA, ACM, (2009)
X. Jin, Y. Zhou, and B. Mobasher. KDD '04: Proceedings of the tenth ACM SIGKDD international conference on Knowledge discovery and data mining, page 197--205. New York, NY, USA, ACM, (2004)