@article{DE_1985_21_2_a7,
     author = {Z. O. Mel'nik},
     title = {A problem with integral constraints for general two-dimensional hyperbolic equations and systems},
     journal = {Differencialʹnye uravneni\^a},
     pages = {246--253},
     publisher = {mathdoc},
     volume = {21},
     number = {2},
     year = {1985},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1985_21_2_a7/}
}