@article{Ragozin:2004,
	author = {E. N. Ragozin and I. I. Sobel’man},
	title = {Free-electron laser: advancement into the X-ray region},
	publisher = {Physics-Uspekhi},
	year = {2004},
	journal = {Phys. Usp.},
	volume = {47},
	number = {2},
	pages = {195-196},
	url = {https://ufn.ru/en/articles/2004/2/g/},
	doi = {10.1070/PU2004v047n02ABEH001755}
}