Li , HongMa , Lilin and Zhu , Wenjing. (2021). Chaotic Behavior and Subharmonic Bifurcations for the Duffing-Van Der Pol Oscillator.
            <i>Journal of Nonlinear Modeling and Analysis</i>. <i>1</i> (2).
            237-250.
         doi:10.12150/jnma.2019.237