1. M. E. Adams and M. Gould, “Posets whose monoids of order-preserving maps are regular,” Order, 6, 195–201 (1989).
2. A. Ya. Aizenshtat, “Generating relations of an endomorphism semigroup of a finite linearly ordered set,” Sib. Mat. Zh., 3, No. 2, 161–169 (1962).
3. A. Ya. Aizenshtat, “Regular endomorphism semigroups of ordered sets,” Uchen. Zap. Leningr. Gos. Ped. Inst., 387, 3–11 (1968).
4. A. H. Clifford and G. B. Preston, The Algebraic Theory of Semigroups, Vols. 1, 2, Amer. Math. Soc., Providence (1961, 1967).
5. L. M. Gluskin, “Isotone transformation semigroups,” Usp. Mat. Nauk, 16, No. 5, 157–162 (1961).