Perestyuk, N. A., and V. Yu. Slyusarchuk. “Periodic Solutions of Nonlinear Differential Equations With Pulse Influence in a Banach Space”. Ukrains’kyi Matematychnyi Zhurnal 47, no. 3 (March 25, 1995): 370–380. Accessed April 11, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/5426.