@article{PismaZhETF.14.449,
    title = {Population Inversion in Solids by Impact Excitation of Impurities},
    author = {Vlasenko, N. A. and Pukhlii, Zh. A.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {14},
    issue = {8},
    pages = {449},
    year = {1971},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_24930.shtml},
}