TY  - JOUR
AU  - A. P. Sadovskii
TI  - A solution of the center and focus problem in a special case
JO  - Differencialʹnye uravneniâ
PY  - 1968
SP  - 943
EP  - 945
VL  - 4
IS  - 5
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DE_1968_4_5_a19/
LA  - ru
ID  - DE_1968_4_5_a19
ER  -