TY  - JOUR
AU  - K. S. Sibirskii
TI  - Conditions for the presence of a simple saddle-center of an autonomous two-dimensional differential system
JO  - Differencialʹnye uravneniâ
PY  - 1986
SP  - 1456
EP  - 1458
VL  - 22
IS  - 8
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DE_1986_22_8_a22/
LA  - ru
ID  - DE_1986_22_8_a22
ER  -