Vitrychenko, I. E. “Critical Cases of the π-Stability of a Nonautonomous Quasilinear Equation of the Nth Order”. Ukrains’kyi Matematychnyi Zhurnal 56, no. 2 (February 25, 2004): 264–270. Accessed April 11, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/3750.