NIZHNIK, L. P. Boundary value problems with singular conditions on boundary components of small dimensions. Methods of Functional Analysis and Topology, [S. l.], v. 7, n. 1, p. 76–81, 2001. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/141. Acesso em: 17 dec. 2025.