Khan, Muhammad Munib. “Variational Iteration Method for the Solution of Differential Equation of Motion of the Mathematical Pendulum and Duffing-Harmonic Oscillator”. Earthline Journal of Mathematical Sciences 2, no. 1 (May 2, 2019): 101-109. Accessed November 22, 2024. https://earthlinepublishers.com/index.php/ejms/article/view/101.