  If the large scale structure of the Universe was created, even partially, via
Zeldovich pancakes, than the fluctuations of the CMB radiation should be formed
due to bulk comptonization of black body spectrum on the contracting pancake.
Approximate formulas for the CMB energy spectrum after bulk comptonization are
obtained. The difference between comptonized energy spectra of the CMB due to
thermal and bulk comptonization may be estimated by comparison of the plots for
the spectra in these two cases.
