Y. M. Berezansky, “Leonid Pavlovych Nyzhnyk (on his 70-th birthday)”, Ukr. Mat. Zhurn., vol. 57, no. 8, pp. 1120–1122, Aug. 2005, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3669