GEORGIEVA, A., and S. KOSTADINOV. “APPROXIMATION METHODS FOR THE SOLUTIONS OF IMPULSE DIFFERENTIAL EQUATIONS”. Tamkang Journal of Mathematics 30, no. 4 (December 1, 1999): 263–269. Accessed May 6, 2024. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4232.