Evtukhov, V. M., and A. A. Stekhun. “Asymptotic Representations of Solutions of One Class of Nonlinear Nonautonomous Differential Equations of the Third Order”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 59, no. 10, Oct. 2007, pp. 1363–1375, https://umj.imath.kiev.ua/index.php/umj/article/view/3395.