@article{DE_1968_4_12_a7,
     author = {N. I. Avdonin},
     title = {The relative position of the separatrices},
     journal = {Differencialʹnye uravneni\^a},
     pages = {2230--2242},
     publisher = {mathdoc},
     volume = {4},
     number = {12},
     year = {1968},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1968_4_12_a7/}
}