HOMOTOPY PERTURBATION METHOD (HPM), ADOMIAN DECOMPOSITION METHOD (ADM) AND COUPLING HPM AND PEM (PARAMETER-EXPANSION METHOD) FOR NONLINEAR OSCILLATOR WITH COORDINATE-DEPENDENT MASS. Far East Journal of Mathematical Sciences (FJMS), [S. l.], v. 142, n. 4, p. 615–637, 2025. DOI: 10.17654/0972087125034. Disponível em: https://pphmjopenaccess.com/fejms/article/view/3277. Acesso em: 5 jan. 2026.