IL’KIV, V.S. The smoothness of solutions of the problems with nonlocal multi-point conditions for strictly hyperbolic equations. Carpathian Mathematical Publications, [S. l.], v. 1, n. 1, p. 47–58, 2009. Disponível em: https://journals.pnu.edu.ua/index.php/cmp/article/view/4003. Acesso em: 24 apr. 2024.