@article{DE_1986_22_8_a22,
     author = {K. S. Sibirskii},
     title = {Conditions for the presence of a simple saddle-center of an autonomous two-dimensional differential system},
     journal = {Differencialʹnye uravneni\^a},
     pages = {1456--1458},
     publisher = {mathdoc},
     volume = {22},
     number = {8},
     year = {1986},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/DE_1986_22_8_a22/}
}