  Measurements sensitive to the structure of both real and virtual photons are
presented and compared to theoretical models with various photon parton
distribution functions (PDFs). Measurements for real photons show a tendency
for the available photon PDFs to be too small to describe the data. For virtual
photons, the photon PDF is seen to decrease with increasing photon virtuality.
In order to describe the data, resolved photon processes are required up to a
photon virtuality of at least 4.5 GeV^2.
