@article{MS2_1954__2_165555,
     author = {Wilhelm Maak},
     title = {Periodizit\"atseigenschaften unit\"ater {Gruppen} in {Hilbertr\"aumen.}},
     journal = {Mathematica Scandinavica},
     pages = {334--344},
     publisher = {mathdoc},
     volume = {2},
     year = {1954},
     zbl = {0057.06802},
     url = {http://geodesic.mathdoc.fr/item/MS2_1954__2_165555/}
}