%0 Journal Article
%A Yu. A. Kravtsov
%T ``Quasi-isotropic'' approximation of geometrical optics
%J Doklady Akademii Nauk
%D 1968
%P 74-76
%V 183
%N 1
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1968_183_1_a18/
%G ru
%F DAN_1968_183_1_a18