Observational signatures of particle acceleration in supernova remnants
  We evaluate the current status of supernova remnants as the sources of
Galactic cosmic rays. We summarize observations of supernova remnants, covering
the whole electromagnetic spectrum and describe what these obser- vations tell
us about the acceleration processes by high Mach number shock fronts. We
discuss the shock modification by cosmic rays, the shape and maximum energy of
the cosmic-ray spectrum and the total energy budget of cosmic rays in and
surrounding supernova remnants. Additionally, we discuss problems with
supernova remnants as main sources of Galactic cosmic rays, as well as
alternative sources.
