Idris, Nur Nasrin Athirah, et al. “Homotopy Analysis Method to Solve Second-Order Nonlinear Ordinary Differential Equations”. Enhanced Knowledge in Sciences and Technology, vol. 1, no. 2, July 2021, pp. 51-59, https://publisher.uthm.edu.my/periodicals/index.php/ekst/article/view/2095.