Ignat’evA. O., & KonosevichВ. I. (1999). On the stability of invariant sets of a system of autonomous differential equations under constantly acting perturbations. Ukrains’kyi Matematychnyi Zhurnal, 51(9), 1287–1291. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/4725