Necessary and sufficient conditions for the existence and uniqueness of bounded solutions of nonlinear differential equations. Neliniini Kolyvannya, [S. l.], v. 2, n. 4, p. 523–539, 1999. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/85. Acesso em: 22 jan. 2026.