Dudzyanyi, S. I., and N. A. Perestyuk. “On the Stability of a Trivial Invariant Torus of One Class of Impulsive Systems”. Ukrains’kyi Matematychnyi Zhurnal 50, no. 3 (March 25, 1998): 338–349. Accessed May 19, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/4935.