GORBACHUK, M. L.; TORBA, S. M. On existence of boundary values of polyharmonic functions. Methods of Functional Analysis and Topology, [S. l.], v. 10, n. 2, p. 4–12, 2004. Disponível em: https://zen.imath.kiev.ua/index.php/mfat/article/view/236. Acesso em: 17 dec. 2025.