V. D. Derech, “On maximal stable orders on an inverse semigroup of finite rank with zero”, Ukr. Mat. Zhurn., vol. 60, no. 8, pp. 1035–1041, Aug. 2008, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3221