Swoboda, Jan Max Planck Institute for Mathematics, Max Planck Society;
Swoboda_spectraloid_2010.pdf (Any fulltext), 187KB
Swoboda, J., & Wimmer, H. K. (2010). Spectraloid operator polynomials, the approximate numerical range and an Eneström-Kakeya theorem in Hilbert space. Studia Mathematica, 198(3), 279-300.