中国科学院数学与系统科学研究院期刊网
AMS
On the Origin and Numerical Range of Bounded Operators
Xiao Hong WU, Jun Jie HUANG, ALATANCANG
Acta Mathematica Sinica . 2019, (10): 1715 -1722 .  DOI: 10.1007/s10114-019-8478-2