KRASNOSELSKY, M. A.; LEVIN, A. Y.; MAMEDOV, Y. D. On estimates of solutions of differential equations of the second order. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 18, n. 1, p. 110–116, 1966. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8660. Acesso em: 6 dec. 2025.