@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/