%0 Journal Article
%A M. A. Krasnosel'skii
%A E. I. Pustyl'nik
%T The use of fractional powers of operators in studying Fourier series of eigenfunctions of differential operators
%J Doklady Akademii Nauk
%D 1958
%P 978-981
%V 122
%N 6
%I mathdoc
%U http://geodesic.mathdoc.fr/item/DAN_1958_122_6_a5/
%G ru
%F DAN_1958_122_6_a5