%0 Journal Article
%A S. D. Shchuko
%T On the problem of distinguishing between a center and a focus
%J Doklady Akademii Nauk
%D 1972
%P 1008-1010
%V 203
%N 5
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1972_203_5_a8/
%G ru
%F DAN_1972_203_5_a8