@article{MM2_1977__21_154466,
     author = {Roswitha Blind},
     title = {Eine {Charaketrisierung} der {Sph\"are} im {E3.}},
     journal = {Manuscripta mathematica},
     pages = {243--254},
     publisher = {mathdoc},
     volume = {21},
     year = {1977},
     zbl = {0366.53032},
     url = {http://geodesic.mathdoc.fr/item/MM2_1977__21_154466/}
}