  The recovering procedure of the electron-phonon interaction (EPI) functions
from the additional nonlinearities of the current-voltage curve ($I-V$ curve)
of point contacts associated with an excess current is considered. The approach
proposed takes into account both inelastic scattering, which causes suppression
of the excess current in the reabsorption of nonequilibrium phonons by
electrons undergoing Andreev reflection (Andreev electrons), and elastic
processes associated with the electron-phonon renormalization of the energy
spectrum in a superconductor. The results obtained are systematically expounded
for both the ballistic contacts, wherein the second derivatives of the $I-V$
curve in the normal state are proportional to the EPI functions, and
inhomogeneous contacts (with dirty constrictions and clean banks), whose second
derivatives in the normal state are either free of phonon singularities or
weakly pronounced.
