1. A. W. Burks, Ed.,Essays on Cellular Automata (University of Illinois Press, Urbana, Illinois, 1970).
2. H. P. Edmundson and I. I. Tung, ?Set-Theoretic Relations between the Class of Probabilistic Languages and the Chomsky Hierarchy,? Technical Report TR-585, Department of Computer Science, University of Maryland (1977).
3. C. A. Ellis, ?Probabilistic Languages and Automata,? Ph.D. Dissertation, University of Illinois (1969).
4. M. Fliess, ?Propriétés Booléennes des langages stochastiques,?Math. Syst. Theory 7:353?359 (1973).
5. J. E. Hopcroft and J. D. Ullman,Formal Languages and Their Relation to Automata (Addison-Wesley, Reading, Massachusetts, 1969).