[1] B. M. Глyшкoв: Cинтeз цифpoвыx aвтoмaтoв. Физмaтгиз, Mocквa 1962.
[2] J. Mareš:
Two Properties of Expressions in a Certain Free Universal Algebra. (In Czech.) Kybernetika 5 (1969), 3, 190-200.
MR 0246808
[3] J. A. Brzozowski:
Derivatives of Regulaг Expressions. Jouгnal of ACM 11 (1964), 481-494.
MR 0174434