@article{PismaZhETF.25.491,
    title = {Direct observation of focusing of acoustic phonons in ruby crystals},
    author = {Akimov, A. V. and Basun, S. A. and Kaplyanskii, A. A. and Rachin, V. A. and Titov, R. A.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {25},
    issue = {10},
    pages = {491},
    year = {1977},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_21469.shtml},
}