TY  - JOUR
AU  - L. A. Cherkas
TI  - An Estimate of the Number of Limit Cycles via Critical Points of Conditional Extremum
JO  - Differencialʹnye uravneniâ
PY  - 2003
SP  - 1334
EP  - 1342
VL  - 39
IS  - 10
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/item/DE_2003_39_10_a4/
LA  - ru
ID  - DE_2003_39_10_a4
ER  -