  The EGRET instrument has measured detailed photon spectra between 30 MeV and
10 GeV, which are represented by means of single power-law fits for sources in
the 3EG catalog. However, various sources show indications of spectral cutoffs
at GeV energies, which are poorly represented by such simple fits. In the case
of well exposed or bright EGRET sources, a description of spectral cutoffs with
more complicated functional forms appears to be applicable. An application for
such multicomponent fits should be seen in extrapolations beyond the energies
accessible to EGRET, i.e. for detectability studies of low-threshold Imaging
Atmospheric Cherenkov Telescopes (IACTs). In cases of unidentified gamma-ray
sources positionally coincident with Supernova remnants, the spectral shape
beyond power-law extrapolations might observationally explain why such
prominent SNRs like gammaCygni, IC 443 and CTA1 have not been detected during
several observation campaigns performed by IACTs over the last years.
