%0 Journal Article
%A È. F. Kirnitskaya
%A K. S. Sibirskii
%T Conditions for two centers for a quadratic differential system
%J Differencialʹnye uravneniâ
%D 1978
%P 1589-1593
%V 14
%N 9
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DE_1978_14_9_a5/
%G ru
%F DE_1978_14_9_a5