@article{PismaZhETF.27.619,
    title = {Concentration of light by inverting its wavefront},
    author = {Pilipetskii, M. F. and Popovichev, V. I. and Ragul'skii, V. V.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {27},
    issue = {11},
    pages = {619},
    year = {1978},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_23786.shtml},
}