PUTRUS, R.; SALEEM, H. The existence and uniqueness of the solutions for a system of some fractional order nonlinear differential equations. Journal of Education and Science, [S. l.], v. 21, n. 1, p. 124–137, 2008. DOI: 10.33899/edusj.2008.51258. Disponível em: https://edusj.uomosul.edu.iq/index.php/edusj/article/view/41418. Acesso em: 10 sep. 2025.