Here we are! Part III—the last part of this volume! Here, we introduce additional tools widely used in the analysis of dynamical systems (specifically the Fourier series, the Fourier and Laplace transforms, and prerequisite material, e.g., complex analysis, i.e., the theory of analytic functions of a complex variable). In addition, we address asymptotic techniques (e.g., multiple scales and normal form) for the solutions of weakly nonlinear dynamical systems, along with computational methods.