KOVTUN, I. I.; FELLER, M. N. Boundary-value problems for a nonlinear hyperbolic equation with Levy Laplaciana. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 64, n. 11, p. 1492–1499, 2012. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2675. Acesso em: 5 dec. 2025.