@article{PismaZhETF.6.619,
    title = {Superradiance at Transitions Terminating at Metastable Levels of Helium and Thallium},
    author = {Isaev, A. A. and Ishchenko, P. I. and Petirash, G. G.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {6},
    issue = {5},
    pages = {619},
    year = {1967},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_25437.shtml},
}