@article{DAN_1982_264_4_a5,
     author = {B. A. Bubnov and V. N. Vragov},
     title = {On the theory of well-posed boundary value problems for some classes of ultrahyperbolic equations},
     journal = {Doklady Akademii Nauk},
     pages = {795--800},
     year = {1982},
     volume = {264},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1982_264_4_a5/}
}