EvtukhovV. M., and Droggina A. V. “Asymptotic Representations of Solutions of Nonautonomous Ordinary Differential Equations”. Ukrains’kyi Matematychnyi Zhurnal 71, no. 12 (December 25, 2019): 1626-1646. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/1006.