On the Structure of the Virtual Compton Amplitude in the Generalized   Bjorken Region: Integral Relations
  A systematic study is performed of the structure of the twist-2 contributions to the virtual Compton amplitude in deep-inelastic non-forward scattering for general spin states in the non-local light cone expansion. The gauge invariance is proven in this approach for the twist-2 contributions for non-forward scattering. Relations are derived between the contributing non-forward amplitudes. 
Johannes Bl\"umlein and Dieter Robaschik