T. Kanungo, and D. Orr. WSDM '09: Proceedings of the Second ACM International Conference on Web Search and Data Mining, page 202--211. New York, NY, USA, ACM, (2009)
E. Agichtein, E. Brill, S. Dumais, and R. Ragno. SIGIR '06: Proceedings of the 29th annual international ACM SIGIR conference on Research and development in information retrieval, page 3--10. New York, NY, USA, ACM, (2006)