@article{DAN_1972_204_2_a4,
     author = {V. A. Kondratiev and S. D. \`Eidel'man and T. G. Pletneva},
     title = {On positive solutions of partial differential equations in a neighborhood of a smooth noncharacteristic hypersurface},
     journal = {Doklady Akademii Nauk},
     pages = {279--282},
     publisher = {mathdoc},
     volume = {204},
     number = {2},
     year = {1972},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1972_204_2_a4/}
}