@article{DE_1988_24_4_a3,
     author = {B. S. Kalitin},
     title = {Pseudostability and first prolongations},
     journal = {Differencialʹnye uravneni\^a},
     pages = {571--574},
     publisher = {mathdoc},
     volume = {24},
     number = {4},
     year = {1988},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1988_24_4_a3/}
}