O. Y. Hryshchenko, D. A. Klyushin, S. I. Lyashko, and I. V. Sergienko, “Ivan Ivanovych Lyashko (on his 90 th birthday)”, Ukr. Mat. Zhurn., vol. 64, no. 11, pp. 1568–1571, Nov. 2012, Accessed: Dec. 06, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/2681