@article{DAN_1992_327_4_a0,
     author = {A. V. Bitsadze},
     title = {On a hyperbolic system of first-order quasilinear equations},
     journal = {Doklady Akademii Nauk},
     pages = {423--427},
     year = {1992},
     volume = {327},
     number = {4},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1992_327_4_a0/}
}