TY  - JOUR
AU  - Takeaki Yamazaki
TI  - On upper and lower bounds of the numerical radius
 and an equality condition
JO  - Studia Mathematica
PY  - 2007
SP  - 83
EP  - 89
VL  - 178
IS  - 1
PB  - mathdoc
UR  - http://geodesic.mathdoc.fr/articles/10.4064/sm178-1-5/
DO  - 10.4064/sm178-1-5
LA  - en
ID  - 10_4064_sm178_1_5
ER  -