1. Hopcroft, J.E., Motwani, R., Ullman, J.D.: Introduction to Automata Theory, Languages, and Computation, 2nd edn. Pearson Education, Boston (2000). ISBN 0-201-44124-1
2. Lecture Notes in Computer Science;R Alur,2006
3. Alur, R., Madhusudan, P.: Adding nesting structure to words. J. ACM 56(3), 1–43 (2009)
4. Lecture Notes in Computer Science;F Neven,2002
5. Hunter, D., Rafter, J., Fawcett, J.: Beginning XML. John Wiley & Sons, New York (2007)