@article{PismaZhETF.67.229,
    title = {Sufficient conditions for the existence of $Q$-balls in gauge theories},
    author = {Kusenko, A. and Shaposhnikov, M. and Tinyakov, P. G.},
    journal = {Письма в ЖЭТФ},
    volume = {67},
    issue = {4},
    pages = {229},
    year = {1998},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_15172.shtml},
}