@article{DE_1991_27_4_a7,
     author = {G. D. Dachev},
     title = {On the existence of smooth solutions of boundary value problems for a class of equations of mixed type},
     journal = {Differencialʹnye uravneni\^a},
     pages = {619--627},
     publisher = {mathdoc},
     volume = {27},
     number = {4},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1991_27_4_a7/}
}