Bilenko, V. I., K. V. Bozhonok, and S. Yu. Dzyadyk. 2019. “Piecewise-Polynomial approximations for the Solutions of Impulsive Differential Equations”. Ukrains’kyi Matematychnyi Zhurnal 71 (2), 168-79. https://umj.imath.kiev.ua/index.php/umj/article/view/1429.