@article{PismaZhETF.94.252,
    title = {Flat bands in topological media},
    author = {HeikkiläT
, T. and Kopnin, N. B. and Volovik, G. E.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {94},
    issue = {3},
    pages = {252},
    year = {2011},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_29480.shtml},
}