1. U. Fano, A.R.P. Rau: Atomic Collisions and Spectra (Academic, New York 1986).
2. J.D. Jackson: Classical Electrodynamics (Wiley, New York 1962).
3. I.N. Levine: Molecular Spectroscopy (Wiley, New York 1975).
4. J.I. Steinfeld: Molecules and Radiation (MIT Press, Boston 1986).
5. For a concise derivation of the X-ray absorption cross section see: J.W. Davenport: Ph.D. Dissertation, University of Pennsylvania (1976) (unpublished).