GorbachukM. L., ZadereiP. V., LukovskyI. O., MitropolskiyY. A., RomanyukA. S., RukasovV. I., SamoilenkoA. M., SerdyukA. S., and ShevchukI. A. “Alexander Ivanovich Stepanets”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 59, no. 12, Dec. 2007, pp. 1722-4, https://umj.imath.kiev.ua/index.php/umj/article/view/3427.