N. BUTRUS, R.; A. AZEEZ, M. Some theorems in existence and oneness of a system of integral - nonlinear differential equations. Journal of Education and Science (JES), [S. l.], v. 18, n. 2, p. 76–89, 2006. DOI: 10.33899/edusj.2006.79261. Disponível em: https://ojs.uomosul.edu.iq/index.php/edusj/article/view/23573. Acesso em: 6 aug. 2025.