%0 Journal Article
%A N. L. Shcheglova
%T A criterion for the coexistence of a center and a focus of the equation $y'=(x+\lambda y+Q_3)/(-y+\lambda x+P_3)$
%J Differencialʹnye uravneniâ
%D 1991
%P 2001-2005
%V 27
%N 11
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DE_1991_27_11_a22/
%G ru
%F DE_1991_27_11_a22