FELLER, M. N. Boundary-value problems for the wave equation with Lévy Laplacian in the Gâteaux class. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 61, n. 11, p. 1564–1574, 2009. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3122. Acesso em: 5 dec. 2025.