Juan E. Napoles Valdes, Luciano M. Lugo Motta Bittencurt, and Paulo M. Guzman. 2015. “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 (4 - E):15-21. http://ijmaa.in/index.php/ijmaa/article/view/521.