“…This has led to, so called, different``versions'' of the MMS method which differ in, for example, whether or not a transformation of time, T = Ot, is used, the way the detuning parameters are introduced (i.e., the way the excitation frequency O is expanded in power series of the perturbation parameter e), and in the way the partial time derivatives for the amplitude and phase of the response main harmonic component are used to obtain the second and higher order steady state response [3±5, 7,8]. Consider, for example, the problem, discussed in detail in reference [3], of obtaining a uniformly valid second order MMS approximation to the steady state primary resonance response of the weakly non-linear oscillator…”