%0 Journal Article
%A E. L. Tonkov
%T The second order periodic equation
%J Doklady Akademii Nauk
%D 1969
%P 296-299
%V 184
%N 2
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1969_184_2_a9/
%G ru
%F DAN_1969_184_2_a9