1. Chacron, M. and G. Thierrin,σ-Reflexive semigroups and rings, Canad. Math. Bull. 15(2), (1972), 185–188.
2. Cherubini Spoletini, A. e A. Varisco,Sui semigruppi fortemente reversibili separativi, Istituto Lombardo (Rend. Sc.) 111, (1977), 31–43.
3. Cherubini Spoletini, A. e A. Varisco,Sui semigruppi i cui sottosemigruppi propri sono t-archimedei, Istituto Lombardo (Rend. Sc.) 112, (1978), 91–98.
4. Chrislock, J.L.,On medial semigroups, J. Algebra 12, (1969), 1–9.
5. Clifford, A.H. and G.B. Preston,The algebraic theory of semigroups, Amer. Mat. Soc., Providence, R. I., Vol. I, (1961).