@article{DAN_1992_325_3_a12,
     author = {A. F. Zubova},
     title = {A study of stability and instability zones for equations of the},
     journal = {Doklady Akademii Nauk},
     pages = {483--485},
     publisher = {mathdoc},
     volume = {325},
     number = {3},
     year = {1992},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DAN_1992_325_3_a12/}
}