L. Ratinov, and D. Roth. CoNLL '09: Proceedings of the Thirteenth Conference on Computational Natural Language Learning, page 147--155. Morristown, NJ, USA, Association for Computational Linguistics, (2009)
J. Finkel, T. Grenager, and C. Manning. Proceedings of the 43nd Annual Meeting of the Association for Computational Linguistics (ACL 2005), page 363--370. (2005)