N. BUTRIS, R.; SHUKER JAMEEL, G. Periodic Solutions for Nonlinear System of Differential Equations of Third Order with Boundary Conditions. Journal of Education and Science (JES), [S. l.], v. 26, n. 1, p. 126–139, 2013. DOI: 10.33899/edusj.2013.89560. Disponível em: https://ojs.uomosul.edu.iq/index.php/edusj/article/view/23242. Acesso em: 6 aug. 2025.