ALIEV, B. A. Asymptotic behavior of the eigenvalues of a boundary-value problem for a second-order elliptic operator-differential equation. Ukrains’kyi Matematychnyi Zhurnal, [S. l.], v. 58, n. 8, p. 1146–1152, 2006. Disponível em: https://umj.imath.kiev.ua/index.php/umj/article/view/3519. Acesso em: 6 dec. 2025.