E. A. Toichkina, “Semigroups of endotopisms of efficient and connected relations”, Ukr. Mat. Zhurn., vol. 68, no. 3, pp. 377–387, Mar. 2016, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/1845