Evtukhov, V. M., & Kas'yanova, V. A. (2005). Asymptotic Behavior of Unbounded Solutions of Essentially Nonlinear Second-Order Differential Equations. I. Ukrains’kyi Matematychnyi Zhurnal, 57(3), 338–355. https://umj.imath.kiev.ua/index.php/umj/article/view/3602