@article{PismaZhETF.60.64,
    title = {Perturbation theory for quasistationary levels},
    author = {Popov, V. S. and Mur, V. D.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {60},
    issue = {1},
    pages = {64},
    year = {1994},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_19977.shtml},
}