M. Rosen-Zvi, T. Griffiths, M. Steyvers, and P. Smyth. Proceedings of the 20th Conference on Uncertainty in Artificial Intelligence, page 487--494. Arlington, Virginia, United States, AUAI Press, (2004)
D. Ramage, D. Hall, R. Nallapati, and C. Manning. Proceedings of the 2009 Conference on Empirical Methods in Natural Language Processing: Volume 1 - Volume 1, page 248--256. Stroudsburg, PA, USA, Association for Computational Linguistics, (2009)