@article{CMH_1969__44_139395,
     author = {Peter Hess},
     title = {Zur {St\"orungstheorie} linearer {Operatoren:} {Relative} {Beschr\"anktheit} und relative {Kompaktheit} von {Operatoren} in {Banachr\"aumen.}},
     journal = {Commentarii mathematici Helvetici},
     pages = {245--248},
     publisher = {mathdoc},
     volume = {44},
     year = {1969},
     zbl = {0181.13705},
     url = {http://geodesic.mathdoc.fr/item/CMH_1969__44_139395/}
}