Analytical study of light ray trajectories in Kerr spacetime in the presence of an inhomogeneous anisotropic plasmaMohsen Fathi, Marco Olivares and J. R. VillanuevaEur. Phys. J. C, 81 11 (2021) 987DOI: https://doi.org/10.1140/epjc/s10052-021-09787-1