@article{PismaZhETF.12.139,
    title = {Direct Observation of Hyperbolic Excitons},
    author = {Subashiev, V. K. and Le Hak Bin, },
    journal = {Письма в ЖЭТФ},
    volume = {12},
    issue = {3},
    pages = {139},
    year = {1970},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_26255.shtml},
}