@article{PismaZhETF.9.315,
    title = {Density of Relict Particles with Zero Rest Mass in the Universe},
    author = {Shvartsman, V. F.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {9},
    issue = {5},
    pages = {315},
    year = {1969},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_25352.shtml},
}