Gluon- vs. Sea quark-Shadowing
  We calculate the shadowing of sea quarks and gluons and show that the shadowing of gluons is {\it not} simply given by the sea quark shadowing, especially at small $x$. The calculations are done in the lab frame approach by using the generalized vector meson dominance model. Here the virtual photon turns into a hadronic fluctuation long before the nucleus. The subsequent coherent interaction with more than one nucleon in the nucleus leads to the depletion $\sigma (\gamma^* A) < A\sigma (\gamma^* N)$ known as shadowing. A comparison of the shadowing of quarks to E665 data for $^{40}Ca$ and $^{207}Pb$ shows good agreement. 
N. Hammon, H. St\"ocker, W. Greiner