Abstract
In this paper the equivalence \(\tilde {\cal Q}^U \) on a semigroup S in terms of a set U of idempotents in S is defined. A semigroup S is called a U-liberal semigroup with U as the set of projections and denoted by S(U) if every \(\tilde {\cal Q}^U \)-class in it contains an element in U. A class of U-liberal semigroups is characterized and some special cases are considered.
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He, Y., Shao, F., Li, Sq. et al. On left C-U-liberal semigroups. Czech Math J 56, 1085–1108 (2006). https://doi.org/10.1007/s10587-006-0081-x
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DOI: https://doi.org/10.1007/s10587-006-0081-x