Quasinormal modes and their anomalous behavior for black holes in f(R) gravity Almendra Aragón, P. A. González, Eleftherios Papantonopoulos and Yerko Vásquez Eur. Phys. J. C, 81 5 (2021) 407 Published online: 10 May 2021 DOI: 10.1140/epjc/s10052-021-09193-7