1. Adair, C.L., Varieties of * orthodox semigroups, Ph.D.Thesis, University of South Carolina (1979).
2. Adair, C.L., Bands with an involution, J. Algebra 75(1982), 297–314.
3. Howie, J.M., An introduction to semigroup theory, Academic Press, London, 1976.
4. Margolis, S.W. and J.C. Meakin, E-unitary inverse monoids and the Cayley graph of a group presentation, preprint.
5. Nordahl, T.E. and H.E. Scheiblich, Regular * semigroups, Semigroup Forum 16(1978), 369–377.