@article{1181072150,
author = {H\"ubner, Matthias},
title = {Spectrum where the Boundary of the Numerical Range is not Round},
journal = {Rocky Mountain J. Math.},
volume = {25},
number = {4},
year = {1995},
pages = { 1351-1355},
language = {en},
url = {http://dml.mathdoc.fr/item/1181072150}
}
Hübner, Matthias. Spectrum where the Boundary of the Numerical Range is not Round. Rocky Mountain J. Math., Tome 25 (1995) no. 4, pp. 1351-1355. http://gdmltest.u-ga.fr/item/1181072150/