[1] Carruth, J.H., Hildebrant, J.A., and Koch, R.J.: The Theory of Topological Semigroups I. Pure and Applied Mathematics series, Marcel Dekker, Inc., New York, 1983. MR 0691307

[2] Clifford, A.H., and Preston, G.B.: The Algebraic Theory of Semigroups I. Math. Surveys, 7, Amer. Math. Soc., 1961. MR 0132791

[3] Tamura, T.: The theory of construction of finite semigroups III. Osaka Math J. 10, 191–204. MR 0102560 | Zbl 0084.02604

[4] Yamada, M.: Construction of finite commutative z-semigroups. Proc, Japan Acad. 40, 94–98. MR 0163975 | Zbl 0121.26903