Volchkov, V. V., V. V. Volchkov, and I. M. Savost’yanova. 2015. “One Problem Connected With the Helgason Support Problem”. Ukrains’kyi Matematychnyi Zhurnal 67 (9), 1189-1200. https://umj.imath.kiev.ua/index.php/umj/article/view/2058.