MITROPOLSKIY, Yu. A.; KHOMA, L. G. The existence of a classical solution to the mixed problem for a linear second-order hyperbolic equation. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 9, p. 1232–1238, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5925. Acesso em: 5 dec. 2025.