“…In recent years, several analytical methods such as homotopy perturbation [1], harmonic balance [2], residue harmonic balance [3], The Hamiltonian approach [4], homotopy analysis [5], max-min approach [6], coupling of homotopy variation [7], iterative homotopy harmonic balance method [8], global residue harmonic balance [9], Fourier series solutions with finite harmonic terms [10], amplitude-frequency formulation [11][12][13], parameter-expansion method [14][15][16][17][18][19], multi-step homotopy analysis method [20], multiple-scales homotopy perturbation method [21][22][23] and the Frobenius-homotopy method [24] have been developed for solving strongly nonlinear oscillators.…”