NedokisV. A., SamoilenkoA. M., and TeplinskyYu. V. 2004. “Truncation Method for Countable-Point Boundary-Value Problems in the Space of Bounded Number Sequences”. Ukrains’kyi Matematychnyi Zhurnal 56 (9), 1203-30. https://umj.imath.kiev.ua/index.php/umj/article/view/3836.