Lower bounds on the eigenvalue ratio with Robin boundary conditions. Gulf Journal of Mathematics, [S. l.], v. 19, n. 2, p. 489–499, 2025. DOI: 10.56947/gjom.v19i2.2825. Disponível em: https://gjom.org/index.php/gjom/article/view/2825. Acesso em: 22 sep. 2026.