@article{JETPL.111.494,
    title = {Effective Group Velocity and Shape of Twin Beams},
    author = {Prudkovskii, P. A.},
    journal = {JETP Lett.},
    volume = {111},
    issue = {8},
    pages = {428},
    year = {2020},
    doi = {10.1134/S0021364020080081},
    url = {http://jetpletters.ru/ps/dx/10.31857/S123456782008011X},
    note = {[Pisma v ZhETF 111, 494 (2020)]}
}