ProsenyukL. G. “Existence and Asymptotic Behavior of Solutions of an $n$-Th-Order Differential Equation Partially Solved With Respect to Derivative”. Ukrains’kyi Matematychnyi Zhurnal, Vol. 46, no. 4, Apr. 1994, pp. 450–453, https://umj.imath.kiev.ua/index.php/umj/article/view/5746.