Echoes of black holes in Einstein-nonlinear electrodynamic theories Aofei Sang, Ming Zhang, Shao-Wen Wei and Jie Jiang Eur. Phys. J. C, 83 4 (2023) 291 Published online: 12 April 2023 DOI: 10.1140/epjc/s10052-023-11448-4