1. S. Eilenberg, Automata, Languages, and Machines, Vol. B, Academic Press (1976).
2. P. A. Grillet, A completion theorem for finitely generated commutative semigroups, J. Algebra, 34 (1975), 25–53.
3. P. A. Grillet, Subcomplete commutative semigroups, Acta Sci. Math. (Szeged), 67 (2001), 601–628.
4. P. A. Grillet, Commutative Semigroups, xiv + 436 pp, Kluwer Acad. Publ. (Dordrecht, 2001).
5. P. A. Grillet, Cancellative coextensions, Acta Sci. Math. (Szeged), 69 (2003), 543–567.