%0 Journal Article
%A S. A. Zolotarev
%T On the problem of distinguishing the center and focus in a certain case
%J Differencialʹnye uravneniâ
%D 1991
%P 1852-1862
%V 27
%N 11
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DE_1991_27_11_a2/
%G ru
%F DE_1991_27_11_a2