R. McDonald, K. Hannan, T. Neylon, M. Wells, and J. Reynar. Proceedings of the Association for Computational Linguistics (ACL), page 432--439. Prague, Czech Republic, Association for Computational Linguistics, (June 2007)
M. Hu, and B. Liu. KDD '04: Proceedings of the tenth ACM SIGKDD international conference on Knowledge discovery and data mining, page 168--177. New York, NY, USA, ACM, (2004)