@article{PismaZhETF.67.124,
    title = {Critical velocity and event horizon in pair-correlated systems with "relativistic" fermionic quasiparticles},
    author = {Kopnin, N. B. and Volovik, G. E.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {67},
    issue = {2},
    pages = {124},
    year = {1998},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_15154.shtml},
}