Rabiner, Lawrence R. 1989. A Tutorial on Hidden Markov Models and Selected Applications in Speech Recognition. Proceedings of the 31st Annual Meeting of the Association for Computational Linguistics , 251-258. Technical Report, Xerox Corporation. Viterbi, A. J. 1967.
Error bounds for convolutional codes and asymptotically optimal decoding algorithm.
Coping with ambiguity and unknown words through probabilistic methods. Computational Linguistics 19.