  Kogan et al. [Phys. Rev. B 80, 014507 (2009)] present a two-band model to
investigate its effect on superconducting properties as, e.g., the superfluid
density, the specific heat, the dependence of the superconducting transition
temperature Tc on the model parameters. Due to a variety of simplifications and
unphysical consequences of those, erroneous results and misleading conclusions
are obtained.
