@article{MM2_1970__2_153995,
     author = {Oswald Giering},
     title = {Die windschiefen {Fl\"achen} konstanter {Dralls} in der {Normalenkongruenz} einer {Fl\"ache.}},
     journal = {Manuscripta mathematica},
     pages = {163--180},
     publisher = {mathdoc},
     volume = {2},
     year = {1970},
     zbl = {0182.54704},
     url = {http://geodesic.mathdoc.fr/item/MM2_1970__2_153995/}
}