@article{TM_1968_103_a11,
     author = {I. M. Petrushko},
     title = {Boundary value problems for equations of mixed type},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     pages = {181--200},
     publisher = {mathdoc},
     volume = {103},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/TM_1968_103_a11/}
}