• Korean Journal of Mathematics
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• v.13 no.2
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• pp.177-182
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• 2005

If a semigroup S has no nontrivial congruences then S is either simple or 0-simple.([2]) By contrast with ring theory, not every congruence on a semigroup is associated with an ideal, hence some simple(or 0-simple) semigroup may have a nontrivial congruence. Thus it is a short note for the characterization of a simple(or 0-simple) semigroup that is congruence-free. A semigroup that has no nontrivial congruences is said to be congruence-free.

• Journal of applied mathematics & informatics
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• v.9 no.1
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• pp.449-458
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• 2002

We shall give a gereralization for a new right congruence induced by right congruences on S and right ideals of S and discuss the radicals associated with automata. Also we shall discuss the relationship between the collection of all right ideals in S and the collection of all right congruences on S.