Xu, Yeyin, and Albert C.J. Luo. “A Series of Symmetric Period-1 Motions to Chaos in a Two-Degree-of-Freedom Van Der Pol-Duffing Oscillator”. Journal of Vibration Testing and System Dynamics 2, no. 2 (June 1, 2018): 119–153. Accessed October 17, 2026. https://lhscientificpublishing.com/index.php/jvtsd/article/view/223.