@article{DE_1972_8_1_a2,
     author = {D. K. Gvazava},
     title = {Certain estimates for equations of mixed type},
     journal = {Differencialʹnye uravneni\^a},
     pages = {17--23},
     publisher = {mathdoc},
     volume = {8},
     number = {1},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1972_8_1_a2/}
}