J. Al-Sawoor, Ann, آن, Merna A. Samarchi, and میرنا. “An Application of He’s Variational Iteration Method for Solving Duffing - Van Der Pol Equation”. AL-Rafidain Journal of Computer Sciences and Mathematics 10, no. 2 (June 25, 2025): 153–163. Accessed August 5, 2025. https://rjps.uomosul.edu.iq/index.php/csmj/article/view/19431.