@article{MM2_1971__5_154077,
     author = {Josef Hoschek},
     title = {Scheitels\"atze f\"ur {Regelfl\"achen.}},
     journal = {Manuscripta mathematica},
     pages = {309--322},
     year = {1971},
     volume = {5},
     zbl = {0223.53010},
     url = {http://geodesic.mathdoc.fr/item/MM2_1971__5_154077/}
}