Parton Distributions in the Photon
  We discuss in detail the photon structure function beyond the leading logarithm approximation. Of special concern is the factorization scheme and the hadronic input; we show how to naturally absorb large terms due to the MSbar factorization scheme in a modified hadronic component. The effect of the charm quark mass threshold is also discussed in relation to the phenomenology. A comparison with data shows that the modified hadronic component can be reasonably described by a VDM-type input. 
P.Aurenche, M.Fontannaz, J.Ph.Guillet