Fossil group origins - IX. Probing the formation of fossil galaxy groups with stellar population gradients of their central galaxiesE. M. Corsini, L. Morelli, S. Zarattini, J. A. L. Aguerri, L. Costantin, E. D’Onghia, M. Girardi, A. Kundert, J. Méndez-Abreu and J. ThomasA&A, 618 (2018) A172DOI: https://doi.org/10.1051/0004-6361/201832625