%0 Journal Article
%A A. I. Tret'yak
%T Necessary conditions for optimality of even order in a
%J Doklady Akademii Nauk
%D 1991
%P 1058-1060
%V 316
%N 5
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1991_316_5_a7/
%G ru
%F DAN_1991_316_5_a7