Consequences of t-channel unitarity for gamma(*)p and gamma(*) gamma(*)   amplitudes
  We show that t-channel unitarity constraints make it possible to obtain the photon-photon cross sections from the photon-proton and proton-proton cross sections, for Q2<150 GeV2. In order to do so, one must postulate the existence of double-pole or triple-pole singularities in the complex j plane. 
J.R. Cudell, E. Martynov and G. Soyez (Liege U.)