Wang, A., and L. Wang. “Congruences on Regular Semigroups With $Q$-Inverse Transversals”. Ukrains’kyi Matematychnyi Zhurnal 68, no. 6 (June 25, 2016): 853-859. Accessed April 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/1884.