%0 Journal Article
%A G. S. Rychkov
%T A proof of the presence of an infinite number of limit cycles for the equation $\ddot y+\mu\ sin$ $(\dot y+\theta )+y=0$
%J Differencialʹnye uravneniâ
%D 1973
%P 1540-1542
%V 9
%N 8
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DE_1973_9_8_a22/
%G ru
%F DE_1973_9_8_a22