RomanyukA. S., SamoilenkoA. M., SerdyukA. S., and SokolenkoI. V. 2012. “International Conference "Theory of Approximation of Functions and Its applications" Dedicated to the 70 Th Birthday of the Corresponding Member of NASU Professor O. I. Stepanets (1942 - 2007)”. Ukrains’kyi Matematychnyi Zhurnal 64 (10), 1438-40. https://umj.imath.kiev.ua/index.php/umj/article/view/2671.