Quantum states of an electromagnetic field interacting with a classical current and their applications to radiation problems / V. G. Bagrov, D. M. Gitman, A. A. Shishmarev, A. J. D. Farias Jr. // Journal of synchrotron radiation. 2020. Vol. 27, P. 4. P. 902-911. URL: http://vital.lib.tsu.ru/vital/access/manager/Repository/vtls:000795560