For the basic understanding, read the followings:

Hidden Markov Models, Theory and Applications

Hidden Markov Models: Estimation and Control (Stochastic Modelling and Applied Probability)

For specific Character recognition, Please follow the

Hidden Markov Models Edited Book by Horst Bunke. Chapter : A 2-D HMM Method for Offline Handwritten Character Recognition

Hope this will help.!

Thanks dileep

The following tutorial is very useful:

http://people.sabanciuniv.edu/berrin/cs512/reading/rabiner-tutorial-on-hmm.pdf

Introductory articles to HMMs:

An introduction to hidden Markov models L Rabiner, BH Juang - ASSP Magazine, IEEE, 1986

A tutorial on hidden Markov models and selected applications in speech recognition L Rabiner - Proceedings of the IEEE, 1989

This material is also found in the book

Fundamentals of speech recognition LR Rabiner, BH Juang - 1993