PROSENYUK, L. G. Existence and asymptotic properties of solutions of a real system of differential equations unresolved with respect to the derivative. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 10, p. 1461–1464, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5952. Acesso em: 5 dec. 2025.