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http://journals.cambridge.org/action/displayAbstract?aid=2888512
Copy and paste this citation
CHI-KWONG LI
and YIU-TUNG POON
(2009).
SPECTRUM, NUMERICAL RANGE AND DAVIS-WIELANDT SHELL OF A NORMAL OPERATOR. Glasgow Mathematical Journal, 51
,
pp 91-100
doi:10.1017/S0017089508004564