@article{GDZPPN002343428, title = {Periodizit\"atseigenschaften unit\"ater Gruppen in Hilbertr\"aumen.}, journal = {Mathematica Scandinavica}, volume = {2}, year = {1954}, pages = {334-344}, zbl = {0057.06802}, url = {http://dml.mathdoc.fr/item/GDZPPN002343428} }
Maak, Wilhelm. Periodizitätseigenschaften unitäter Gruppen in Hilberträumen.. Mathematica Scandinavica, Tome 2 (1954) pp. 334-344. http://gdmltest.u-ga.fr/item/GDZPPN002343428/