@article{DAN_1991_319_1_a31,
     author = {Yu. G. Smirnov},
     title = {The {Fredholm} property of the problem of diffraction by a flat},
     journal = {Doklady Akademii Nauk},
     pages = {147--149},
     publisher = {mathdoc},
     volume = {319},
     number = {1},
     year = {1991},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1991_319_1_a31/}
}