%0 Journal Article
%A V. V. Amel'kin
%T On the question of the isochronism of the center of two-dimensional analytic differential systems
%J Differencialʹnye uravneniâ
%D 1977
%P 971-980
%V 13
%N 6
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DE_1977_13_6_a0/
%G ru
%F DE_1977_13_6_a0