@article{DAN_1964_154_4_a2,
     author = {S. A. Gal'pern and V. E. Kondrashov},
     title = {The {Cauchy} problem for a differential operator decomposing into wave factors},
     journal = {Doklady Akademii Nauk},
     pages = {757--759},
     publisher = {mathdoc},
     volume = {154},
     number = {4},
     year = {1964},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1964_154_4_a2/}
}