Putrus, Raad, and Hamsa Saleem. “The Existence and Uniqueness of the Solutions for a System of Some Fractional Order Nonlinear Differential Equations”. Journal of Education and Science (JES) 21, no. 1 (March 1, 2008): 124–137. Accessed August 6, 2025. https://ojs.uomosul.edu.iq/index.php/edusj/article/view/23280.