ZAVOROTINSKII, A. V. On Elliptic Boundary-Value Problems with Small Parameter and Additional Functions on the Boundary of a Domain. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 66, n. 9, p. 1269–1275, 2014. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/2218. Acesso em: 5 dec. 2025.