Petryshyn, R. I., and Sopronyuk Т. M. “Exponential Estimate for the Fundamental Matrix of a Linear Impulsive System”. Ukrains’kyi Matematychnyi Zhurnal 53, no. 8 (August 25, 2001): 1101–1108. Accessed December 6, 2025. https://umj.imath.kiev.ua/index.php/umj/article/view/4329.