@article{PismaZhETF.92.889,
    title = {Generation of two-photon correlation in a four-level system},
    author = {Ma, Y. H. and Wu, E.},
    journal = {Письма в ЖЭТФ},
    volume = {92},
    issue = {12},
    pages = {889},
    year = {2010},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_29084.shtml},
}