  The problem of the uniqueness of solutions during the evaluation of primary
energy spectra in the knee region using an extensive air shower (EAS) data set
and the EAS inverse approach is investigated. It is shown that the unfolding of
primary energy spectra in the knee region leads to mutually compensative pseudo
solutions. These solutions may be the reason for the observed disagreements in
the elementary energy spectra of cosmic rays in the 1-100 PeV energy range
obtained from different experiments.
