TY  - JOUR
AU  - S. A. Zolotarev
TI  - On the problem of distinguishing the center and focus in a certain case
JO  - Differencialʹnye uravneniâ
PY  - 1991
SP  - 1852
EP  - 1862
VL  - 27
IS  - 11
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DE_1991_27_11_a2/
LA  - ru
ID  - DE_1991_27_11_a2
ER  -