SHKLYAR, A. Ya. Correctness of the Cauchy problem for trinomial higher-order operator differential equations. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 5, p. 704–714, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5857. Acesso em: 7 apr. 2025.