T. Rattenbury, N. Good, and M. Naaman. Proceedings of the 30th annual international ACM SIGIR conference on Research and development in information retrieval, page 103--110. ACM, (2007)
H. Li, and N. Abe. Proceedings of the 17th international conference on Computational linguistics-Volume 2, page 749--755. Association for Computational Linguistics, (1998)