@article{DE_1985_21_4_a1,
     author = {A. V. Zhevnyak},
     title = {The direction vector method for investigating the stability of singular points of nonlinear systems. {I.} {Theory}},
     journal = {Differencialʹnye uravneni\^a},
     pages = {562--572},
     publisher = {mathdoc},
     volume = {21},
     number = {4},
     year = {1985},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1985_21_4_a1/}
}