GORBATENKO, Ya. V. Existence and uniqueness of mild solutions of second order semilinear differential equations in Banach space. Methods of Functional Analysis and Topology, [S. l.], v. 17, n. 1, p. 1–9, 2011. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/465. Acesso em: 16 dec. 2025.