Juan E. Napoles Valdes, Luciano M. Lugo Motta Bittencurt, and Paulo M. Guzman. “A Note on the Continuability of Solutions of a Perturbed Second Order Nonlinear Differential Equation of Lienard Type”. International Journal of Mathematics And its Applications 3, no. 4 - E (December 30, 2015): 15–21. Accessed May 19, 2024. http://ijmaa.in/index.php/ijmaa/article/view/521.