PODLIPENKO, Yu. K. Boundary-value problems for the helmholtz equation in an angular domain. II. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 45, n. 4, p. 500–519, 1993. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/5838. Acesso em: 5 dec. 2025.