@article{PismaZhETF.15.520,
    title = {Spin-echo Enhancement by Double-frequency Pumping},
    author = {Danilov, V. V. and Sugakov, V. I. and Tychinskii, A. V.},
    journal = {Письма в ЖЭТФ},
    volume = {15},
    issue = {9},
    pages = {520},
    year = {1972},
    doi = {},
    url = {http://jetpletters.ru/ps/0/article_26647.shtml},
}