@article{MM2_1977__23_154521,
     author = {Rolf Schneider},
     title = {\"Uber {Tangentialk\"orper} der {Kugel.}},
     journal = {Manuscripta mathematica},
     pages = {269--278},
     publisher = {mathdoc},
     volume = {23},
     year = {1977},
     zbl = {0383.52004},
     url = {http://geodesic.mathdoc.fr/item/MM2_1977__23_154521/}
}