1. Arbib, M. A. [Editor]: Algebraic theory of machines, languages and semigroups. New York: Academic Press 1968.
2. Cannon, J. J.: Computers in group theory: A survey. Comm. ACM12, 1, 3?12 (January 1969).
3. Cannon, J. J. Dimino, L. A.: Implementation of the Todd-Coxeter algorithm. In preparation.
4. Clifford, A. H., Preston, J. B.: The algebraic theory of semigroups, volume 1. Providence, Rhode Island: Amer. Math. Soc. 1964.
5. Coxeter, H. S. M., Moser, W. O. J.: Generators and relations for discrete groups. Second edition. Berlin-Heidelberg-New York: Springer 1965.