References
- C. R. Acad. Paris v.252 Demi-groups quasi-inversif Calais, J.
- The Algebraic Theory of Semigroups, Vol. I. Clifford, A.H.;Preston, G.B.
- Bull. Amer. Math. Soc. v.58 Associated groups for a semigroup Good, R.A.;Hughes, D.R.
- Techniques of Semigroup Theory Higgins, P.
- Publ. Math. Debrecen v.16 On bi-ideals and quasi-ideals in semigroups Kapp, K.M.
- Acta. Sci. Math. v.22 Generalized ideals in semigroups Lajos, S.
- Publ. Math. Debrecen v.4 Uber die quasiideale von halbgruppen Steinfeld, O.
- Quasi-ideals in Rings and Semigroups Steinfeld, O.