@article{PismaZhETF.21.144,
    title = {"Softening" of phonon spectrum in semiconductors of the $Pb_{1-x}Sn_x$ Te system on going to the gapless state},
    author = {Nikolaev, I. N. and Shotov, A. P. and Volkov, A. F. and Mar'in, V. P.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {21},
    issue = {2},
    pages = {144},
    year = {1975},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_22271.shtml},
}