@article{MMO_1967_16_a4,
     author = {S. A. Gal'pern and V. E. Kondra\v{s}ov},
     title = {The {Cauchy} problem for differential operators which decompose into wave factors},
     journal = {Trudy Moskovskogo matemati\v{c}eskogo ob\^{s}estva},
     pages = {109--136},
     publisher = {mathdoc},
     volume = {16},
     year = {1967},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MMO_1967_16_a4/}
}