M. F. Gorodnii and V. N. Romanenko, “Approximation of a bounded solution of one difference equation with unbounded operator coefficient by solutions of the corresponding boundary-value problems”, Ukr. Mat. Zhurn., vol. 52, no. 4, pp. 548–552, Apr. 2000, Accessed: Apr. 09, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4445