Please cite at least one of the following articles if FEFF is used in published work.
A.L. Ankoudinov, PhD Thesis, Relativistic Spin-dependent X-ray Absorption Theory, University of Washington, (1996). There you will find a review of x-ray absorption theory, a whole chapter of information about FEFF7 for expert users, examples of the code applications, and a full list of the FEFF7 program tree.