@article{DE_1984_20_1_a6,
     author = {S. K. Kulazhanov},
     title = {The spectrum of a mixed problem for an equation of mixed type},
     journal = {Differencialʹnye uravneni\^a},
     pages = {56--60},
     publisher = {mathdoc},
     volume = {20},
     number = {1},
     year = {1984},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1984_20_1_a6/}
}