@article{DAN_1990_310_5_a13,
     author = {O. A. Godin},
     title = {Estimates for phase and group velocities of acoustic normal waves},
     journal = {Doklady Akademii Nauk},
     pages = {1084--1089},
     publisher = {mathdoc},
     volume = {310},
     number = {5},
     year = {1990},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1990_310_5_a13/}
}