%0 Journal Article
%A V. V. Amel'kin
%T Letter to the editors: “On the question of the isochrony of the center of two-dimensional analytic differential systems” (Differencial'nye Uravnenija 13 (1977), no. 6, 971–980)
%J Differencialʹnye uravneniâ
%D 1977
%P 1537
%V 13
%N 8
%U http://geodesic.mathdoc.fr/item/DE_1977_13_8_a28/
%G ru
%F DE_1977_13_8_a28