@article{PORMA_1942__3_1_114594,
     author = {von Neumann, John},
     title = {Approximative properties of matrices of high finite order},
     journal = {Portugaliae mathematica},
     pages = {1--62},
     publisher = {mathdoc},
     volume = {3},
     number = {1},
     year = {1942},
     mrnumber = {0006137},
     zbl = {0026.23302},
     language = {en},
     url = {http://geodesic.mathdoc.fr/item/PORMA_1942__3_1_114594/}
}