V. V. Doroshenko, “Most Transformation Semigroups Are Free”, Mat. Zametki, 87:3 (2010), 464–467; Math. Notes, 87:3 (2010), 436–439
2005
2.
Vadym Doroshenko, “Generators and relations for the semigroups of increasing functions on $\mathbb N$ and $\mathbb Z$”, Algebra Discrete Math., 2005, no. 4, 1–15
