S. Argamon, K. Bloom, A. Esuli, and F. Sebastiani. Proceedings of the 3rd Language and Technology Conference (LTC'07), page 369--373. Poznan, Poland, (2007)
B. Pang, and L. Lee. ACL '04: Proceedings of the 42nd Annual Meeting on Association for Computational Linguistics, page 271. Morristown, NJ, USA, Association for Computational Linguistics, (2004)