Khan, Md Mamun Ur Rashid, and Goutam Saha. “Analytical Solution of Liénard Differential Equation Using Homotopy Perturbation Method”. GANIT: Journal of Bangladesh Mathematical Society 39 (November 19, 2019): 87–100. Accessed September 18, 2024. https://banglajol.info/index.php/GANIT/article/view/44160.