[A tutorial on hidden Markov models and selected applications in speech recognition](http://luthuli.cs.uiuc.edu/~daf/courses/Signals%20AI/Papers/HMMs/0.pdf)
[A tutorial on hidden Markov models and selected applications in speech recognition](http://www.cs.cmu.edu/~cga/behavior/rabiner1.pdf)
[Weighted Finite-State Transducers in Speech Recognition](http://www.cs.nyu.edu/~mohri/pub/csl01.pdf)