@article{PismaZhETF.90.167,
    title = {Two-level systems and mass deficit in quantum solids},
    author = {Korshunov, S. E.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {90},
    issue = {2},
    pages = {167},
    year = {2009},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_28565.shtml},
}