@article{DE_1988_24_12_a16,
     author = {N. Radjabov},
     title = {A second-order equation of hyperbolic type with two singular lines},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2129--2133},
     publisher = {mathdoc},
     volume = {24},
     number = {12},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1988_24_12_a16/}
}