@article{DE_1974_10_2_a0,
     author = {A. F. Andreev},
     title = {The exceptional direction of an $n$th order system at a stationary point},
     journal = {Differencialʹnye uravneni\^a},
     pages = {187--194},
     publisher = {mathdoc},
     volume = {10},
     number = {2},
     year = {1974},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1974_10_2_a0/}
}