BOGOLYUBOV, A.; MALYKH, M.; PANIN, A. Two-sided estimates for the eigenvalues of the Laplace operator with Dirichlet boundary conditions and their application to problems in the mathematical theory of waveguides. Numerical Methods and Programming (Vychislitel’nye Metody i Programmirovanie), [S. l.], v. 10, n. 19, p. 83–93, 2009. Disponível em: https://en.num-meth.ru/index.php/journal/article/view/350. Acesso em: 20 apr. 2024.