%0 Journal Article
%A N. I. Avdonin
%T Certain tests for the existence and absence of closed trajectories of a certain system of differential equations
%J Differencialʹnye uravneniâ
%D 1968
%P 639-645
%V 4
%N 4
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DE_1968_4_4_a6/
%G ru
%F DE_1968_4_4_a6