1. A. H. Clifford and G. B. Preston, Algebraic Theory of Semigroups, Vols. 1, 2, Amer. Math. Soc., 1964, 1967.
2. E. Hewitt and H. S. Zuckerman, “The l1-algebra of a commutative semigroup,” Trans. Am. Math. Soc., 83, 70–97 (1956).
3. J.-L. Loday, “Dialgebras,” in: Dialgebras and Related Operads, Lect. Notes Math., Vol. 1763, Springer, Berlin (2001), pp. 7–66.
4. J.-L. Loday and M. O. Ronco, “Trialgebras and families of polytopes,” in: P. Goerss, ed., Homotopy Theory: Relations with Algebraic Geometry, Group Cohomology, and Algebraic K-Theory. Papers from the Int. Conf. on Algebraic Topology, Northwestern Univ., Evanston, IL, USA, March 24–28, 2002, Contemp. Math., Vol. 346, Amer. Math. Soc., Providence (2004), pp. 369–398.
5. D. McLean, “Idempotent semigroups,” Am. Math. Mon., 61, 110–113 (1954).