S. Mohammad, B. Dorr, M. Egan, A. Hassan, P. Muthukrishan, V. Qazvinian, D. Radev, und D. Zajic. Proceedings of Human Language Technologies: The 2009 Annual Conference of the North American Chapter of the Association for Computational Linguistics, Seite 584--592. Stroudsburg, PA, USA, Association for Computational Linguistics, (2009)
M. Burghardt, M. Heckner, und C. Wolff. Volume 4 von Library and Information Science, Kapitel 2, Seite 19--46. Emerald Group Publishing Limited, (2012)