KUZHEL, S. A. Nonlocal perturbations of the radial wave equation. Lax-Phillips approach. Methods of Functional Analysis and Topology, [S. l.], v. 8, n. 2, p. 59–68, 2002. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/184. Acesso em: 17 dec. 2025.