BerezanskyY. M., GorbachukV. I., GorbachukM. L., KostyuchenkoA. G., Kuzhel’S. A., MarchenkoV. O., SamoilenkoA. M., SamoilenkoY. S., and KhruslovE. Y. “Leonid Pavlovych Nyzhnyk (on His 70-Th Birthday)”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 57, no. 8, Aug. 2005, pp. 1120-2, https://umj.imath.kiev.ua/index.php/umj/article/view/3669.