@article{PismaZhETF.26.200,
    title = {Cosmological limits on the masses of neutral leptons},
    author = {Vysotskii, M. I. and Dolgov, A. D. and Zel'dovich, Ya. B.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {26},
    issue = {3},
    pages = {200},
    year = {1977},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_20858.shtml},
}