[1] A. H. Clifford, G. B. Preston: The Algebraic Theory of Semigroups, I. Providence, A.M.S., 1961.

[2] A. H. Clifford, G. B. Preston: The Algebraic Theory of Semigroups, II. Providence, A.M.S., 1967.

[3] С. Eberhart L. Kinch, W. Williams: Idempotent-generated regular semigroups. J. Austral. Math. Soc., Vol. 15 (1973), pp. 27-34. DOI 10.1017/S1446788700012726 | MR 0320185

[4] R. S. Feigenbaum: Kernels of regular semigroup homomorphisms. Dissertation, Univ. of South Carolina, 1975.

[5] D. G. Fitz-Gerald: On inverse of products of idempotents in regular semigroups. J. Austral Math. Soc., V 13 (1972), pp. 335-337. DOI 10.1017/S1446788700013756 | MR 0306366

[6] T. E. Hall: On regular semigroups. J. Algebra, V 24 (1973), pp. 1-24. DOI 10.1016/0021-8693(73)90150-6 | MR 0310098 | Zbl 0262.20074

[7] J. M. Howie, G. Lallement: Certain fundamental congruences on a regular semigroup. Proc. Glasgow Math. Assoc., Vol. 7 (1966), pp. 145-159. DOI 10.1017/S2040618500035334 | MR 0197598 | Zbl 0136.26701

[8] F. W. Levi: On semigroups. Bull. Calcutta Math. Soc., Vol. 36 (1944), pp. 141-146. MR 0011694 | Zbl 0061.02405

[9] F. E. Masat: Right group and group congruences on a regular semigroup. Duke Math. J., Vol. 40 (1973), pp. 393-402. DOI 10.1215/S0012-7094-73-04031-3 | MR 0318378 | Zbl 0267.20057

[10] F. E. Masat: The minimum reflexive semigroup generated by the set of idempotents of a regular semigroup. Semigroup Forum, Vol. 15 (1978), pp. 387-388. MR 0486241

[11] R. R. Stoll: Homomorphisms of a semigroup onto a group. Amer. J. Math., Vol. 73 (1951), pp. 475-481. DOI 10.2307/2372188 | MR 0041128 | Zbl 0042.25304