J. Breese, D. Heckerman, and C. Kadie. Proceedings of the Fourteenth conference on Uncertainty in artificial intelligence, page 43--52. Morgan Kaufmann Publishers Inc., (1998)
T. Mikolov, W. Yih, and G. Zweig. Proceedings of the 2013 Conference of the North American Chapter of the Association for Computational Linguistics: Human Language Technologies, page 746--751. (2013)