The Parton Content of Virtual Photons
  The QCD treatment of the parton structure of virtual photons is briefly recalled, and possible limitations and open questions are pointed out. Various models for these densities are compared, completed by a short discussion of the treatment of heavy flavors. Finally, different ways to measure the parton distributions of virtual photons in e^+e^- and ep experiments are summed up. 
M. Stratmann (Durham Univ.)