@article{PismaZhETF.37.471,
    title = {Perturbation theory for Rydberg states},
    author = {Kazantsev, A. P. and Pokrovskii, V. L.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {37},
    issue = {10},
    pages = {471},
    year = {1983},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_22861.shtml},
}