Oleksandr Ivanovych Stepanets’ (on the 70 th anniversary of his birthday) - Gorbachuk, M. L.; Zaderei, P. V.; Lukovsky, I. O.; Makarov, V. L.; Motornyi, V. P.; Romanyuk, A. S.; Samoilenko, A. M.; Serdyuk, A. S.; Sharko, V. V. (Ukrains’kyi Matematychnyi Zhurnal, 2012)