@article{PismaZhETF.9.364,
    title = {Optical Frequency Standard with Nonlinear Absorbing Gas Cell},
    author = {Letokhov, V. S. and Chebotaev, V. B.},
    journal = {πΙΣΨΝΑ Χ φότζ},
    volume = {9},
    issue = {6},
    pages = {364},
    year = {1969},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_25364.shtml},
}