Sharp Upper Estimates for the First Eigenvalue of a Jacobi Type Operator. Extracta Mathematicae, [S. l.], v. 31, n. 1, p. 69–88, 2016. Disponível em: https://revista-em.unex.es/index.php/EM/article/view/2605-5686.31.1.69. Acesso em: 25 may. 2026.