  The first differential cross section for Mott scattering of a Dirac-Volkov
electron is reviewed. The expression (26) derived by Szymanowski et al.
[Physical Review A {\bf 56}, 3846,(1997)] is corrected. In particular, we
disagree with the expression of $(\frac{d\sigma}{d\Omega})$ they obtained and
we give the exact coefficients multiplying the various Bessel functions
appearing in the scattering differential cross section.
