@article{DAN_1988_301_6_a13,
     author = {A. A. Spektor},
     title = {Qualitative properties and behavior in time of the solutions of},
     journal = {Doklady Akademii Nauk},
     pages = {1337--1340},
     publisher = {mathdoc},
     volume = {301},
     number = {6},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1988_301_6_a13/}
}