Komarenkо A. N. Problem of eigenvalues with a parameter under boundary value conditions for elliptical equations degenerating on part of the region boundary . Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 18, n. 6, p. 3–11, 1966. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/8455. Acesso em: 6 dec. 2025.