Effective spectrum width of the synchrotron radiation V. G. Bagrov, D. M. Gitman, A. D. Levin, A. S. Loginov and A. D. Saprykin Eur. Phys. J. C, 75 11 (2015) 555 Published online: 25 November 2015 DOI: 10.1140/epjc/s10052-015-3798-6