@article{DE_1983_19_1_a3,
     author = {D. K. Gvazava},
     title = {Problems with initial and characteristic conditions for hyperbolic equations with a nonlinear principal part},
     journal = {Differencialʹnye uravneni\^a},
     pages = {22--27},
     publisher = {mathdoc},
     volume = {19},
     number = {1},
     year = {1983},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1983_19_1_a3/}
}