HOMOTOPY PERTURBATION METHOD (HPM), ADOMIAN DECOMPOSITION METHOD (ADM) AND COUPLING HPM AND PEM (PARAMETER-EXPANSION METHOD) FOR NONLINEAR OSCILLATOR WITH COORDINATE-DEPENDENT MASS. FJMS [Internet]. 2025 Sep. 12 [cited 2026 Jan. 5];142(4):615-37. Available from: https://pphmjopenaccess.com/fejms/article/view/3277