Hopcroft, J. E., Motwani, R., & Ullman, J. D. (2006). Introduction to Automata Theory, Languages, and Computation (3rd ed.). Pearson Education.

• Comprehensive coverage of NFA to regular expression conversion and state elimination algorithm
• Chapter 3: Regular Expressions and Languages - detailed treatment of equivalence proofs

Sipser, M. (2012). Introduction to the Theory of Computation (3rd ed.). Course Technology.

• Clear exposition of regular expression and finite automata equivalence
• Chapter 1: Regular Languages - fundamental concepts and conversion algorithms

Lewis, H. R., & Papadimitriou, C. H. (1997). Elements of the Theory of Computation (2nd ed.). Prentice Hall.

• Mathematical foundations of regular language theory and state elimination
• Chapter 2: Finite Automata and Regular Expressions - rigorous treatment of equivalence