@article{DAN_1960_132_5_a4,
     author = {S. A. Gal'pern},
     title = {Lacunae of non-hyperbolic equations},
     journal = {Doklady Akademii Nauk},
     pages = {990--993},
     publisher = {mathdoc},
     volume = {132},
     number = {5},
     year = {1960},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1960_132_5_a4/}
}