This document contains a more detailed description of the ENZ-diffraction theory and clarifies the special features and potential applications of the theory. The contents of this document are the following:

 - A short description of the basic diffraction integral

 - Zernike representation of pupil functions

 - The propagation from the pupil to the focal region

 - Solving the aberration retrieval problem using the ENZ-approach

 - Advanced ENZ-theory

 - A survey of the literature on the subject

 - Current research and future extensions of the ENZ-approach

 - Application of the ENZ-approach to acoustical diffraction problems (ANZ)

 - A listing of the ENZ-publications

For the details of the application of the theory like the numerical implementation, convergence issues, high-numerical aperture complications, vector diffraction theory etc., the reader can consult bibliographic references that are introduced in this text and in the bibliography section of this webpage.