Comment on `Origin of combination frequencies in quantum magnetic   oscillations of two-dimensional multiband metals' by T. Champel [Phys. Rev. B   65, 153403 (2002); cond-mat/0110154]
  We analyze the applicability of our analytical theory of combination harmonics in canonical low-dimensional multi-band Fermi liquids, which was recently criticized by Champel (Phys. Rev. B 65, 153403 (2002)). It is shown that his claim that our analytical theory does not apply at low temperatures and in clean samples, is incorrect. We demonstrate that the analytical theory of combination harmonics is in excellent agreement with the exact numerical results even at zero temperature and for clean systems, which are the most challenging for an analytical description. 
A.S. Alexandrov and A.M. Bratkovsky