@article{PismaZhETF.9.221,
    title = {Two-photon Absorption in Germanium},
    author = {Zubov, B. V. and Kulevskii, L. A. and Makarov, V. P. and Murina, T. M. and Prokohrov, A. M.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {9},
    issue = {4},
    pages = {221},
    year = {1969},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_25313.shtml},
}