Kozubovskaya, I.G. (1971) “On defence of theses at Academic Council of the Institute of Mathematics of the Academy of Sciences of the Ukrainian SSR in 1970—1971 ”, Ukrains’kyi Matematychnyi Zhurnal, 23(4), pp. 564–568. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/8594 (Accessed: 6 December 2025).