@article{DE_1979_15_1_a17,
     author = {S. S. Kharibegashvili},
     title = {Characteristic problem for second-order strictly hyperbolic systems with two independent variables},
     journal = {Differencialʹnye uravneni\^a},
     pages = {142--152},
     publisher = {mathdoc},
     volume = {15},
     number = {1},
     year = {1979},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1979_15_1_a17/}
}