Evtukhov, V. M., and V. A. Kas'yanova. “Asymptotic Behavior of Unbounded Solutions of Essentially Nonlinear Second-Order Differential Equations. I”. Ukrains’kyi Matematychnyi Zhurnal 57, no. 3 (March 25, 2005): 338–355. Accessed April 11, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/3602.