BUTYRIN, A. A. On the behavior of solutions of operator-differential equations at infinity. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 46, n. 7, p. 809–813, 1994. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5671. Acesso em: 6 dec. 2025.