@article{RM_1977_32_2_a21,
     author = {N. A. Shananin},
     title = {On necessary conditions for the local solvability of equations of quasiprincipal type},
     journal = {Trudy Matematicheskogo Instituta imeni V.A. Steklova},
     publisher = {mathdoc},
     volume = {32},
     number = {2},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/RM_1977_32_2_a21/}
}