A Unique Atom in [C(E),C_a(E)]
Pei Huisheng · Journal of Mathematical Research and Exposition · 2001
A congruence C. (E) on the semigroup TE(X) is observed in this paper where E is an arbitrary non-trivial equivalence on the set X. It is proved that C. (E) is a unique atom in the complete sublattice [C(E),C. (E)] of the congruence lattice of T.(X).