%0 Journal Article
%A V. M. Babich
%A B. M. Levitan
%T Problem of focusing and the asymptotics of the spectral function of the Laplace--Beltrami operator.~I
%J Zapiski Nauchnykh Seminarov POMI
%D 1978
%P 3-19
%V 78
%I mathdoc
%U http://geodesic.mathdoc.fr/item/ZNSL_1978_78_a0/
%G ru
%F ZNSL_1978_78_a0