Existence of Solutions for Fractional Differential Equations Involving Two Riemann-Liouville Fractional Orders. Analysis in Theory and Applications, [S. l.], v. 34, n. 3, p. 253–274, 2018. DOI: 10.4208/ata.OA-2017-0021. Disponível em: https://global-sci.com/index.php/ata/article/view/15711. Acesso em: 5 dec. 2025.