GERSHTEIN, L. M. On the solvability of a complete second-order differential equation in Banach space. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 10, p. 1449–1454, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5950. Acesso em: 11 apr. 2025.