@article{MZ_1971__123_171624,
     author = {Bernd Knauer},
     title = {\"Uber das {Galerkinverfahren} bei {Eigenwertproblemen} unbeschr\"ankter {Operatoren.}},
     journal = {Mathematische Zeitschrift},
     pages = {113--121},
     publisher = {mathdoc},
     volume = {123},
     year = {1971},
     zbl = {0211.44502},
     url = {http://geodesic.mathdoc.fr/item/MZ_1971__123_171624/}
}