1. An embedding theorem for weakly inverse semigroups;Brown, M. R.;Semigroup Forum,1971
2. Mathematical Surveys, No. 7;Clifford, A. H.,1961
3. On regular semigroups whose idempotents form a subsemigroup;Hall, T. E.;Bull. Austral. Math. Soc.,1969
4. The structure of inverse ideal-simple 𝑜𝑚𝑒𝑔𝑎-semigroups;Kočin, B. P.;Vestnik Leningrad. Univ.,1968
5. A generalization of the Rees theorem in semigroups;Lallement, Gérard;Acta Sci. Math. (Szeged),1969