@article{JRAM_1976__0286_0287_151778,
     author = {Wolfgang Spiegel},
     title = {Zur {Minkowski-Additivit\"at} bestimmter {Eik\"orperabbildungen.}},
     journal = {Journal f\"ur die reine und angewandte Mathematik},
     pages = {164--168},
     publisher = {mathdoc},
     volume = {0286_0287},
     year = {1976},
     zbl = {0333.52003},
     url = {http://geodesic.mathdoc.fr/item/JRAM_1976__0286_0287_151778/}
}