M. U. Akhmetov, “On the expansion of solutions to differential equations with discontinuous right-hand side in a series in initial data and parameters”, Ukr. Mat. Zhurn., vol. 45, no. 5, pp. 715–717, May 1993, Accessed: Apr. 13, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5858