Comatrix Corings and Galois Comodules over Firm Rings
  We give a notion of a comatrix coring which embodies all former constructions and, what is more interesting, leads to the formulation of a notion of Galois coring and the statement of a Faithfully Flat Descent Theorem that generalize the previous versions. 
J. Gomez-Torrecillas and J. Vercruysse