Scattering problems on a perturbation of a part of the boundary. Neliniini Kolyvannya, [S. l.], v. 2, n. 4, p. 448–464, 1999. Disponível em: https://twinhead.imath.kiev.ua/index.php/nosc/article/view/80. Acesso em: 22 jan. 2026.