@article{MZ_1942__47_168954,
     author = {H., Hadwiger},
     title = {\"Uber die {Konvergenzarten} unendlicher {Reihen} im {Hilbertschen} {Raum}},
     journal = {Mathematische Zeitschrift},
     pages = {325--329},
     publisher = {mathdoc},
     volume = {47},
     year = {1942},
     zbl = {0025.15602},
     url = {http://geodesic.mathdoc.fr/item/MZ_1942__47_168954/}
}