%0 Journal Article
%A K. S. Sibirskii
%T Centroaffine invariant center and simple saddle-center conditions for a quadratic differential system
%J Doklady Akademii Nauk
%D 1985
%P 819-823
%V 285
%N 4
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1985_285_4_a10/
%G ru
%F DAN_1985_285_4_a10