GorbachukT. V., and PerestyukN. A. “On the Existence of Discontinuous Limit Cycles for One System of Differential Equations With Pulse Influence”. Ukrains’kyi Matematychnyi Zhurnal 49, no. 8 (August 25, 1997): 1127–1134. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5105.