R. Baeza-Yates, and A. Tiberi. KDD '07: Proceedings of the 13th ACM SIGKDD international conference on Knowledge discovery and data mining, page 76--85. New York, NY, USA, ACM, (2007)
S. Banerjee, K. Ramanathan, and A. Gupta. SIGIR '07: Proceedings of the 30th annual international ACM SIGIR conference on Research and development in information retrieval, page 787--788. New York, NY, USA, ACM, (2007)