Covariant extension of the GPD overlap representation at low Fock states N. Chouika, C. Mezrag, H. Moutarde and J. Rodríguez-Quintero Eur. Phys. J. C, 77 12 (2017) 906 Published online: 26 December 2017 DOI: 10.1140/epjc/s10052-017-5465-6