@article{MZ_1963__82_170193,
     author = {Helmut H. Schaefer},
     title = {Spektraleigenschaften positiver linearer {Operatoren.}},
     journal = {Mathematische Zeitschrift},
     pages = {303--313},
     publisher = {mathdoc},
     volume = {82},
     year = {1963},
     zbl = {0151.19801},
     url = {http://geodesic.mathdoc.fr/item/MZ_1963__82_170193/}
}