%0 Journal Article
%A V. S. Nustrov
%T The periodic solutions of systems that are close to nonlinear systems in the case of principal resonance
%J Izvestiâ vysših učebnyh zavedenij. Matematika
%D 1970
%P 63-69
%N 3
%I mathdoc
%U http://geodesic.mathdoc.fr/item/IVM_1970_3_a9/
%G ru
%F IVM_1970_3_a9