@article{PismaZhETF.10.56,
    title = {Origin of Background X-Radiation},
    author = {Longair, M. S. and Syunyaev, R. A.},
    journal = {Письма в ЖЭТФ},
    volume = {10},
    issue = {1},
    pages = {56},
    year = {1969},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_25682.shtml},
}