Recke, L., and A. M. Samoilenko. “Conditions for Synchronization of One Oscillation System”. Ukrains’kyi Matematychnyi Zhurnal 57, no. 7 (July 25, 2005): 922–945. Accessed April 11, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/3654.