BogolyubovA. N., ValeyevK. G., and TamrazovP. M. “On the 75th Birthday of Vyacheslav Alekseevich Dobrovol’skii”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 46, no. 10, Oct. 1994, p. 1409, https://umj.imath.kiev.ua/index.php/umj/article/view/5621.