1. Introduction to the Theory of Finite-State Machines;Gill,1962
2. An Introduction to Mathematical Machine Theory;Ginsburg,1962
3. Unsolved problems in the enumeration of graphs;Harary;Hung. Acad. Sci. Ser. A,1960
4. Unsolved problems in the enumeration of graphs;Harary;Hung. Acad. Sci. Ser. A,1960
5. A Census of Finite Automata;Harrison,1963