@article{PismaZhETF.45.91,
    title = {Relaxation of two-level systems and sound absorption in metallic glasses},
    author = {Kagan, Yu. and Prokof'ev, N. V.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {45},
    issue = {2},
    pages = {91},
    year = {1987},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_18683.shtml},
}