@article{MOMA_1981__91_178024,
     author = {Wolfgang K\"uhnel},
     title = {Zur inneren {Kr\"ummung} der zweiten {Grundform.}},
     journal = {Monatshefte f\"ur Mathematik},
     pages = {241--252},
     publisher = {mathdoc},
     volume = {91},
     year = {1981},
     zbl = {0449.53043},
     url = {http://geodesic.mathdoc.fr/item/MOMA_1981__91_178024/}
}