@article{GDZPPN00231925X,
title = {The Relative Spectrum of Elements in a Real Banach Algebra.},
journal = {Mathematische Annalen},
volume = {250},
year = {1980},
pages = {113-134},
zbl = {0421.46042},
url = {http://dml.mathdoc.fr/item/GDZPPN00231925X}
}
Hile, G.N.; Pfaffenberger, W.E. The Relative Spectrum of Elements in a Real Banach Algebra.. Mathematische Annalen, Tome 250 (1980) pp. 113-134. http://gdmltest.u-ga.fr/item/GDZPPN00231925X/