Boichuk О. A. and R. F. Khrashchevskaya, “Weakly nonlinear boundary-value problems for differential systems with pulse influence”, Ukr. Mat. Zhurn., vol. 45, no. 2, pp. 221–225, Feb. 1993, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5801