C. Zinn, J. Moore, and M. Core. ITS '02: Proceedings of the 6th International Conference on Intelligent Tutoring Systems, page 574--584. London, UK, Springer-Verlag, (2002)
M. Buckley, and M. Wolska. Proceedings of the 22nd International Conference on Computational Linguistics - Volume 1, page 73--80. Stroudsburg, PA, USA, Association for Computational Linguistics, (2008)