VitrychenkoI. E. “On Stability of the Trivial Solution of a Nonautonomous Quasilinear System Whose Characteristic Equation Has Multiple Roots”. Ukrains’kyi Matematychnyi Zhurnal 46, no. 8 (August 25, 1994): 1072–1079. Accessed July 27, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5660.