Boichuk О. A., V. F. Zhuravlev, and Pokutnyi О. О., “Normally solvable operator equations in a Banach space”, Ukr. Mat. Zhurn., vol. 65, no. 2, pp. 163–174, Feb. 2013, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/2411