@article{DAN_1980_250_5_a1,
     author = {G. D. Dachev},
     title = {On some boundary value problems for a class of equations of mixed type},
     journal = {Doklady Akademii Nauk},
     pages = {1037--1040},
     publisher = {mathdoc},
     volume = {250},
     number = {5},
     year = {1980},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1980_250_5_a1/}
}