V. M. Sel’kin, “Minimal Hereditary ω-Local Non-ℌ-Formations”, Ukr. Mat. Zhurn., vol. 54, no. 3, pp. 373–380, Mar. 2002, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4073