@article{PismaZhETF.11.254,
    title = {Electron Energy Levels at Z > 137},
    author = {Popov, V. S.},
    journal = {Письма в ЖЭТФ},
    volume = {11},
    issue = {5},
    pages = {254},
    year = {1970},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_26105.shtml},
}