VoskresenskiiE. V. “Some Applications of the Comparison Principle in the Theory of Perturbed Systems”. Ukrains’kyi Matematychnyi Zhurnal 46, no. 9 (September 25, 1994): 1255–1260. Accessed November 24, 2024. https://umj.imath.kiev.ua/index.php/umj/article/view/5642.