J. Al-Sawoor, A., آن, M. 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, vol. 10, no. 2, June 2025, pp. 153-6, https://rjps.uomosul.edu.iq/index.php/csmj/article/view/19431.