Boichuk О. A., “Nonlinear boundary-value problems for systems of ordinary differential equations”, Ukr. Mat. Zhurn., vol. 50, no. 2, pp. 162–171, Feb. 1998, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/4951