Pafyk, S. P., & Yakovets, V. P. (2013). On the structure of the general solution and conditions of solvability of the Cauchy problem for degenerate linear systems of higher-order differential equations. *Ukrainsâ€™kyi Matematychnyi Zhurnal*, *65*(2), 296-305. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/2419