Mean value theorem, Ultra Mittag-Leffler function and convergence of successive approximations for fractional differential equations. Nonlinear Studies, [S. l.], v. 15, n. 3, 2008. Disponível em: https://www.nonlinearstudies.com/index.php/nonlinear/article/view/77. Acesso em: 14 jan. 2026.