@article{PismaZhETF.22.32,
    title = {Photon echo in $CaWO_4$ : $Nd^{3+}$},
    author = {Samartsev, V. V. and Usmanov, R. G. and Khad'yev, I. Kh.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {22},
    issue = {1},
    pages = {32},
    year = {1975},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_23249.shtml},
}