@article{1195520010, author = {Furuta, Takayuki and Nakamoto, Ritsuo}, title = {On the numerical range of an operator}, journal = {Proc. Japan Acad.}, volume = {47}, number = {10}, year = {1971}, pages = { 279-284}, language = {en}, url = {http://dml.mathdoc.fr/item/1195520010} }
Furuta, Takayuki; Nakamoto, Ritsuo. On the numerical range of an operator. Proc. Japan Acad., Tome 47 (1971) no. 10, pp. 279-284. http://gdmltest.u-ga.fr/item/1195520010/