DorogovtsevA. A., KopytkoB., KorolyukV. S., MitropolskiyY. A., SamoilenkoA. M., SytayaG. N. and SkorokhodA. V. (2002) “Mykola Ivanovych Portenko (On His 60th Birthday)”, Ukrains’kyi Matematychnyi Zhurnal, 54(2), pp. 147-148. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/4050 (Accessed: 27July2024).