Completely Regular Semigroups for Which Every Congruence on Each 𝒟-Class Extends to a Congruence on the Whole Semigroup
Zhengpan Wang, Houyi Yu · Communications in Algebra · 2014
In 1999, M. Petrich and N. R. Reilly proposed some problems in their monograph “Completely regular semigroups,” one of which is: Characterize those completely regular semigroups S with the property that every congruence on every 𝒟-class extends to a congruence on S. The problem is solved in this paper.