@article{DAN_1958_123_2_a5,
     author = {M. A. Krasnosel'skii and A. I. Perov},
     title = {On a certain principle of the existence of bounded, periodical and almost periodical solutions to systems of ordinary differential equations},
     journal = {Doklady Akademii Nauk},
     pages = {235--238},
     publisher = {mathdoc},
     volume = {123},
     number = {2},
     year = {1958},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1958_123_2_a5/}
}