@article{DAN_1976_226_1_a7,
     author = {I. M. Karasev},
     title = {The first boundary value problem for an equation with nonnegative characteristic form in the spaces
},
     journal = {Doklady Akademii Nauk},
     pages = {38--39},
     publisher = {mathdoc},
     volume = {226},
     number = {1},
     year = {1976},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1976_226_1_a7/}
}