@article{PismaZhETF.25.456,
    title = {Are additional heavy quarks necessary to explain the observed behavior of R(s)?},
    author = {Kuz'min, V. A. and Tavkhelidze, A. N. and Chetyrkin, K. G.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {25},
    issue = {9},
    pages = {456},
    year = {1977},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_21460.shtml},
}