Relative time delay in a spinning black hole as a diagnostic for no-hair theoremRamil N. Izmailov, Eduard R. Zhdanov, Arunava Bhadra and Kamal K. NandiEur. Phys. J. C, 79 2 (2019) 105DOI: https://doi.org/10.1140/epjc/s10052-019-6618-6