O. P. Svistun, “On the existence of piecewise-continuous separatrix curves for a certain class of pulse systems”, Ukr. Mat. Zhurn., vol. 46, no. 5, pp. 580–585, May 1994, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5720