Mapping nonlinear gravity into General Relativity with nonlinear electrodynamics Victor I. Afonso, Gonzalo J. Olmo, Emanuele Orazi and Diego Rubiera-Garcia Eur. Phys. J. C, 78 10 (2018) 866 Published online: 27 October 2018 DOI: 10.1140/epjc/s10052-018-6356-1