@article{MAN_1957__134_160599,
     author = {W. B\"orsch-Supan},
     title = {Obere {Schranken} f\"ur den gr\"o{\ss}ten {Eigenwert} eines vollstetigen selbstadjungierten {Operators.}},
     journal = {Mathematische Annalen},
     pages = {453--457},
     publisher = {mathdoc},
     volume = {134},
     year = {1957},
     zbl = {0081.34103},
     url = {http://geodesic.mathdoc.fr/item/MAN_1957__134_160599/}
}