N. Chomsky and M. P. Schützenberger. The algebraic theory of context-free languages. Computer programming and formal systems, edited by P. Braffort and D. Hirschberg, Studies in logic and the foundations of mathematics, North-Holland Publishing Company, Amsterdam1963, pp. 118–161.
1967 ◽
Vol 32
(3)
◽
pp. 388-389