Mykola Ivanovych Portenko (on his 75th birthday)

Dorogovtsev, A. A., B. Kopytko, and M. M. Osipchuk. “Mykola Ivanovych Portenko (on His 75th Birthday)”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 69, no. 12, Dec. 2017, pp. 1714-6, https://umj.imath.kiev.ua/index.php/umj/article/view/1814.