@article{MOMA_1985__100_178249,
     author = {Hans G\"unther Kopetzky},
     title = {\"Uber das {Approximationsspektrum} des {Einheitskreises.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {211--214},
     publisher = {mathdoc},
     volume = {100},
     year = {1985},
     zbl = {0575.10027},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1985__100_178249/}
}