The light speed versus the observer: the Kennedy–Thorndike test from GRAAL-ESRF V. G. Gurzadyan and A. T. Margaryan Eur. Phys. J. C, 78 8 (2018) 607 Published online: 30 July 2018 DOI: 10.1140/epjc/s10052-018-6080-x