Vyatchaninov, O. V., and M. F. Gorodnii. “On the Boundedness of One Recurrent Sequence in a Banach Space”. Ukrains’kyi Matematychnyi Zhurnal 61, no. 9 (September 25, 2009): 1293-1296. Accessed January 18, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/3100.