ZHUKOVA , G. S. On a differential equation with perturbation at the highest derivative. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 40, n. 4, p. 417–424, 1988. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/9174. Acesso em: 6 dec. 2025.