Doroshenko, V. V. (2009) “On semigroups of order-preserving transformations of countable linearly ordered sets”, Ukrains’kyi Matematychnyi Zhurnal, 61(6), pp. 723-732. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/3055 (Accessed: 25April2024).