@article{PismaZhETF.46.81,
    title = {Zeros in the fermion spectrum in superfluid systems as diabolical points},
    author = {Volovik, G. E.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {46},
    issue = {2},
    pages = {81},
    year = {1987},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_18512.shtml},
}