TY  - JOUR
AU  - Bonsall, F. F.
TI  - The numerical range of an element of a normed algebra
JO  - Glasgow mathematical journal
PY  - 1969
SP  - 68
EP  - 72
VL  - 10
IS  - 1
UR  - http://geodesic.mathdoc.fr/articles/10.1017/S0017089500000562/
DO  - 10.1017/S0017089500000562
ID  - 10_1017_S0017089500000562
ER  -