@article{DAN_1961_137_5_a14,
     author = {V. A. Pliss},
     title = {The existence of periodic solutions of certain non-linear systems},
     journal = {Doklady Akademii Nauk},
     pages = {1060--1062},
     publisher = {mathdoc},
     volume = {137},
     number = {5},
     year = {1961},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1961_137_5_a14/}
}