Boichuk О. A.; KHRASHCHEVSKAYA, R. F. Weakly nonlinear boundary-value problems for differential systems with pulse influence. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 2, p. 221–225, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5801. Acesso em: 11 apr. 2025.