Two-photon exchange contributions to elastic ep scattering in the non-local field formalism P. Jain, S.D. Joglekar and S. Mitra Eur. Phys. J. C, 52 2 (2007) 339-355 Published online: 06 September 2007 DOI: 10.1140/epjc/s10052-007-0395-3