1. N. E. Kobrinskii and B. A. Trakhtenbrot, Introduction to the Theory of Finite Automata [in Russian], Fizmatgiz, Moscow (1962).
2. V. M. Glushkov, Synthesis of Digital Automata [in Russian], Fizmatgiz, Moscow (1962).
3. J. R. Jump, ?A note on iterative decomposition of finite automata,? Inf. Control, No. 15 (1969).
4. J. Hartmanis and R. E. Stearns, The Algebraic Structure Theory of Sequential Machines, Prentice-Hall, New York (1966).
5. G. C. Bacon, ?The decomposition of stochastic automata,? Inf. Control, No. 7 (1964).