In this report a general formulation will be used to demonstrate three aspects of inverse scattering theory: the use of a ptioti information, the mathematical structure of inverse scattering theory, and the construction of more complex models from simpler models. First, the periodic and resonance properties of the scattering data are used to determine the periodicity of a structure. A prioti information about this structure enables the use of an iterative method to determine the amplitude of this periodicity. Second, the analytic properties of the scattering data are used to determine the permittivity of an inhomogeneous and dispersive region. A prioti information about the dispersion relation is essential for this method; in principle this mathematical method is "exact". Third, the first two methods are combined to investigate more complicated scattering data produced by approximately periodic or almost physical models.