%0 Journal Article
%A Bonsall, F. F.
%T The numerical range of an element of a normed algebra
%J Glasgow mathematical journal
%D 1969
%P 68-72
%V 10
%N 1
%U http://geodesic.mathdoc.fr/articles/10.1017/S0017089500000562/
%R 10.1017/S0017089500000562
%F 10_1017_S0017089500000562