Shklyar, A.Y. (1993) “Correctness of the Cauchy problem for trinomial higher-order operator differential equations”, Ukrains’kyi Matematychnyi Zhurnal, 45(5), pp. 704–714. Available at: https://umj.imath.kiev.ua/index.php/umj/article/view/5857 (Accessed: 7 April 2025).