Romanyuk, A. S., V. S. Romanyuk, V. V. Savchuk, A. M. Samoilenko, A. S. Serdyuk, and I. V. Sokolenko. “Oleksandr Ivanovych Stepanets’ (on His 75th Birthday)”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 69, no. 5, May 2017, p. 579, https://umj.imath.kiev.ua/index.php/umj/article/view/1718.