The Eigenvalues of a Class of Elliptic Differential Operators. Journal of Partial Differential Equations, [S. l.], v. 36, n. 1, p. 58–67, 2023. DOI: 10.4208/jpde.v36.n1.4. Disponível em: https://www.global-sci.com/index.php/jpde/article/view/4389. Acesso em: 5 dec. 2025.