@article{MZ_1933__37_168481,
     author = {Th. Kaluza},
     title = {Elementarer {Beweis} einer {Vermutung} von {K.} {Friedrichs} und {H.} {Lewy.}},
     journal = {Mathematische Zeitschrift},
     pages = {689--697},
     publisher = {mathdoc},
     volume = {37},
     year = {1933},
     language = {de},
     url = {http://geodesic.mathdoc.fr/item/MZ_1933__37_168481/}
}