@article{1102866809, author = {Shiu, Elias S. W.}, title = {Commutators and numerical ranges of powers of operators.}, journal = {Pacific J. Math.}, volume = {67}, number = {2}, year = {1976}, pages = { 517-523}, language = {en}, url = {http://dml.mathdoc.fr/item/1102866809} }
Shiu, Elias S. W. Commutators and numerical ranges of powers of operators.. Pacific J. Math., Tome 67 (1976) no. 2, pp. 517-523. http://gdmltest.u-ga.fr/item/1102866809/