GershteinL. M. (1993) “On the solvability of a complete second-order differential equation in Banach space”, Ukrains’kyi Matematychnyi Zhurnal, 45(10), pp. 1449–1454. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/5950 (Accessed: 6October2024).