@article{DAN_1964_157_4_a9,
     author = {A. I. Perov},
     title = {Topological characteristics of solutions of higher-dimensional differential equations},
     journal = {Doklady Akademii Nauk},
     pages = {791--794},
     publisher = {mathdoc},
     volume = {157},
     number = {4},
     year = {1964},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1964_157_4_a9/}
}