@article{DE_1968_4_9_a11,
     author = {M. M. Smirnov},
     title = {The first boundary value problem for a certain equation of mixed type},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1663--1666},
     publisher = {mathdoc},
     volume = {4},
     number = {9},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1968_4_9_a11/}
}