%0 Journal Article
%A L. A. Cherkas
%T An Estimate of the Number of Limit Cycles via Critical Points of Conditional Extremum
%J Differencialʹnye uravneniâ
%D 2003
%P 1334-1342
%V 39
%N 10
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DE_2003_39_10_a4/
%G ru
%F DE_2003_39_10_a4