References

1. Sipser, Michael. Introduction to the Theory of Computation. Third Boston, MA: Course Technology, 2013.
2. Dexter C. Kozen. 1997. Automata and Computability (1st. ed.). Springer-Verlag, Berlin, Heidelberg.
3. Hopcroft, John E. and Ullman, Jeff D.. Introduction to Automata Theory, Languages, and Computation. Addison-Wesley Publishing Company, 1979.