Metric-affine bumblebee gravity: classical aspects Adrià Delhom, J. R. Nascimento, Gonzalo J. Olmo, A. Yu. Petrov and Paulo J. Porfírio Eur. Phys. J. C, 81 4 (2021) 287 Published online: 04 April 2021 DOI: 10.1140/epjc/s10052-021-09083-y