1. Clarke, G.T., Monzo, R.A.R.: A generalisation of the concept of an inflation of a semigroup. Semigroup Forum 60, 172–186 (2000)
2. Golubov, E.A., Sapir, M.V.: Residually small varieties of semigroups. Izv. Vyss. Ucebn. Zaved. Mat. 11, 21–29 (1982) (in Russian). Engl. translation: Sov. Math. (Izv. VUZ) 26(11), 25–36 (1982)
3. Gerhard, J.A.: Semigroups with an idempotent power. I. Word problems. Semigroup Forum 14, 137–141 (1977)
4. Murskiı̌, V.L.: Examples of varieties of semigroups. Mat. Zametki 3, 663–670 (1968) (in Russian). Engl. translation: Math. Notes 3, 423–427 (1968)
5. Petrich, M., Reilly, N.R.: Completely Regular Semigroups. Wiley, New York (1999)