GORODNII, M. F. Existence of solutions of boundary-value problems corresponding to a certain difference equation in a Banach space. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 3, p. 431–435, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5826. Acesso em: 5 dec. 2025.