4.1 Introduction4.2 Amplitude and Frequency Determination4.3 Equivalent Linearisation4.4 Hilbert Transform4.5 Time‐Varying Linear Approximation4.6 Short Time Fourier Transform4.7 Pinpointing Bifurcations4.8 Limit Cycle Study4.9 Poincaré Sections4.10 Stability of Periodic Solutions4.11 Concluding RemarksReferences