%0 Journal Article
%A A. Ya. Kovalenko
%T Perturbation of the periodic solutions of differential equations in the case when the spectrum of the monodromy operator of the generating equation contains~1
%J Izvestiâ vysših učebnyh zavedenij. Matematika
%D 1971
%P 44-49
%N 7
%I mathdoc
%U http://geodesic.mathdoc.fr/item/IVM_1971_7_a5/
%G ru
%F IVM_1971_7_a5