On nilpotency of the syntactic monoid of a language. (English)
Ito, Masami (ed.) et al., Words, languages and combinatorics II. Proceedings of the 2nd international conference, Kyoto, Japan, August 25-28, 1992. Singapore: World Scientific. 279-293 (1994).
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The local and global varieties induced by nilpotent monoids. (English)
RAIRO, Inf. Théor. Appl. 20, 339-355 (1986).
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