Boichuk О. A. Nonlinear boundary-value problems for systems of ordinary differential equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 50, n. 2, p. 162–171, 1998. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4951. Acesso em: 5 dec. 2025.