[1] CLIFFORD A. H., PRESTON G. B.:
The algebгaic theoгy of Semigroups I. Math. Suгveys 7, Pгovidence, 1961.
MR 0132791
[2] GROŠEK O., SATKO L.:
A new notion in the theoгy of Semigгoup. Semigгoup Foгum, 20, 1980, 233-240.
MR 0582229
[3] TAMURA T., HAMILTON H. B.:
Commutative semigroups with greatest group-homomorphism. Proc. Japan Acad., 47, 1971, 671-675.
MR 0304526 |
Zbl 0244.20076
[5] ŠULKA R.:
The minimal right A-ideal of the free semigroup on a coutable set. Math. Slovaca 32, 1982, 301-304.
MR 0670007