Mitropolskiy, Y. A., I. O. Parasyuk, A. M. Samoilenko, and N. I. ShkiI. “Nikolai Perestyuk (60th Birthday)”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 58, no. 1, Jan. 2006, pp. 113-4, https://umj.imath.kiev.ua/index.php/umj/article/view/3437.