@article{PismaZhETF.18.160,
    title = {Energy spectrum of free excitons in germanium},
    author = {Gershenzon, E. M. and Gol'tsman, G. and Ptitsina, N. G.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {18},
    issue = {3},
    pages = {160},
    year = {1973},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_27627.shtml},
}