KHOMA, N. H.; KHOMA, L. G. A linear periodic boundary-value problem for a second-order hyperbolic equation. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 51, n. 2, p. 281–284, 1999. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/4611. Acesso em: 14 apr. 2025.