GorodniiM. F., and RomanenkoV. N. “Approximation of a Bounded Solution of One Difference Equation With Unbounded Operator Coefficient by Solutions of the Corresponding Boundary-Value Problems”. Ukrains’kyi Matematychnyi Zhurnal 52, no. 4 (April 25, 2000): 548-552. Accessed September 1, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4445.