  Recent observations with atmospheric Cherenkov telescope systems such as
H.E.S.S. and MAGIC have revealed a large number of new sources of
very-high-energy (VHE) gamma-rays from 100 GeV - 100 TeV, mostly concentrated
along the Galactic plane. At lower energies (100 MeV - 10 GeV) the
satellite-based instrument EGRET revealed a population of sources clustering
along the Galactic Plane. Given their adjacent energy bands a systematic
correlation study between the two source catalogues seems appropriate. Here,
the populations of Galactic sources in both energy domains are characterised on
observational as well as on phenomenological grounds. Surprisingly few common
sources are found in terms of positional coincidence and spectral consistency.
These common sources and their potential counterparts and emission mechanisms
will be discussed in detail. In cases of detection only in one energy band, for
the first time consistent upper limits in the other energy band have been
derived. The EGRET upper limits are rather unconstraining due to the
sensitivity mismatch to current VHE instruments. The VHE upper limits put
strong constraints on simple power-law extrapolation of several of the EGRET
spectra and thus strongly suggest cutoffs in the unexplored energy range from
10 GeV - 100 GeV. Physical reasons for the existence of cutoffs and for
differences in the source population at GeV and TeV energies will be discussed.
Finally, predictions will be derived for common GeV - TeV sources for the
upcoming GLAST mission bridging for the first time the energy gap between
current GeV and TeV instruments.
