@article{PismaZhETF.1.5,
    title = {Stimulated emission of $Ho^{3+}$ in $CaF_2$ at $\lambda$ = 5512 $\AA$},
    author = {Voron'ko, Yu. K. and Kaminskii, A. A. and Osiko, V. V. and Prokhorov, A. M.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {1},
    issue = {1},
    pages = {5},
    year = {1965},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_24280.shtml},
}