%0 Journal Article
%A M. Sh. Birman
%T Perturbation of the spectrum of a singular elliptic operator under variation of the boundary and boundary conditions
%J Doklady Akademii Nauk
%D 1961
%P 761-763
%V 137
%N 4
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1961_137_4_a0/
%G ru
%F DAN_1961_137_4_a0