@article{PismaZhETF.9.537,
    title = {Asymptotic Lower Bound for the Scattering-amplitude Phase in the t-Plane},
    author = {Tverdokhlebov, A. N.},
    journal = {Письма в ЖЭТФ},
    volume = {9},
    issue = {9},
    pages = {537},
    year = {1969},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_26796.shtml},
}