@article{DE_1977_13_5_a4,
     author = {B. P. Demidovich and Yu. V. Malyshev},
     title = {Further development of the theorem of {N.\,G.~{\v} {C}etaev} on the instability of motion},
     journal = {Differencialʹnye uravneni\^a},
     pages = {841--847},
     publisher = {mathdoc},
     volume = {13},
     number = {5},
     year = {1977},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1977_13_5_a4/}
}