@article{MAN_1980__250_163415,
     author = {G.N. Hile and W.E. Pfaffenberger},
     title = {The {Relative} {Spectrum} of {Elements} in a {Real} {Banach} {Algebra.}},
     journal = {Mathematische Annalen},
     pages = {113--134},
     publisher = {mathdoc},
     volume = {250},
     year = {1980},
     zbl = {0421.46042},
     url = {http://geodesic.mathdoc.fr/item/MAN_1980__250_163415/}
}