@article{DE_1974_10_12_a9,
     author = {A. V. Bitsadze and A. M. Nakhushev},
     title = {On the theory of equations of mixed type in multidimensional domains},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2184--2191},
     publisher = {mathdoc},
     volume = {10},
     number = {12},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1974_10_12_a9/}
}