1. D.Albert and J.Rhodes, “Undecidability of the identity problem for finite semigroups with applications” (preprint, 1986).
2. C.Ash, “Finite semigroups with commuting idempotents,” (preprint, 1986).
3. Springer Lecture Notes in Math;SI Adian,1979
4. J.-C.Birget, S.Margolis, and J.Rhodes, “Finite semigroups whose idempotents commute or form a subsemigroup”, in this volume.
5. J.-C.Birget and J.Rhodes, “Almost finite expansions of arbitrary semigroups,” Journal of Pure & Applied Algebra 32 (1984), 239–287.