P. F. Samusenko and N. I. ShkiI, “On asymptotic formulas for solutions of systems of linear differential equations with a degerate matrix with derivatives”, Ukr. Mat. Zhurn., vol. 48, no. 9, pp. 1278–1285, Sep. 1996, Accessed: Feb. 17, 2026. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/5241