TY  - JOUR
AU  - A. P. Sadovskii
TI  - The problem of the center and focus for analytic systems with a zero linear part. II
JO  - Differencialʹnye uravneniâ
PY  - 1989
SP  - 950
EP  - 956
VL  - 25
IS  - 6
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DE_1989_25_6_a5/
LA  - ru
ID  - DE_1989_25_6_a5
ER  -