  We have rederived the controversial influence functional approach of Golubev
and Zaikin (GZ) for interacting electrons in disordered metals in a way that
allows us to show its equivalence, before disorder averaging, to diagrammatic
Keldysh perturbation theory. By representing a certain Pauli factor (1-2 rho)
occuring in GZ's effective action in the frequency domain (instead of the time
domain, as GZ do), we also achieve a more accurate treatment of recoil effects.
With this change, GZ's approach reproduces, in a remarkably simple way, the
standard, generally accepted result for the decoherence rate. -- The main text
and appendix A.1 to A.3 of the present paper have already been published
previously; for convenience, they are included here again, together with five
additional, lengthy appendices containing relevant technical details.
