@article{DAN_1957_112_4_a5,
     author = {A. I. Polak},
     title = {On sufficient and necessary conditions for complete approximative solvability of equations of a very general nature},
     journal = {Doklady Akademii Nauk},
     pages = {587--590},
     publisher = {mathdoc},
     volume = {112},
     number = {4},
     year = {1957},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1957_112_4_a5/}
}