P. F. Samusenko, “Asymptotic integration of singularly perturbed systems of hyperbolic-type partial differential equations with degeneration”, Ukr. Mat. Zhurn., vol. 63, no. 5, pp. 668–685, May 2011, Accessed: Feb. 16, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/2752