The Components of the $\gamma^*\gamma^*$ Cross Section
  We extend our previous treatment of $\gamma^*p$ cross section based on Gribov's hypothesis to the case of photon-photon scattering. With the aid of two parameters, determined from experimental data, we separate the interactions into two categories corresponding to short ("soft") and long ("hard") distance processes. The photon-photon cross section, thus, receives contributions from three sectors, soft-soft, hard-hard and hard-soft. The additive quark model is used to describe the soft-soft sector, pQCD the hard-hard sector, while the hard-soft sector is determined by relating it to the $\gamma^{*}$p system. We calculate and display the behaviour of the total photon-photon cross section and it's various components and polarizations for different values of energy and virtuality of the two photons, and discuss the significance of our results. 
E. Gotsman, E. Levin, U. Maor and E. Naftali (Tel-Aviv U.)