TY  - JOUR
AU  - L. A. Cherkas
TI  - The absence of limit cycles for a certain differential equation that has a structurally unstable focus
JO  - Differencialʹnye uravneniâ
PY  - 1970
SP  - 779
EP  - 783
VL  - 6
IS  - 5
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DE_1970_6_5_a1/
LA  - ru
ID  - DE_1970_6_5_a1
ER  -