VedernikovV. A., and KoptyukhD. G. “Hereditary Critical Ω-Compositional Formations”. Ukrains’kyi Matematychnyi Zhurnal 53, no. 5 (May 25, 2001): 579-588. Accessed November 25, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4281.