@article{GDZPPN002216388, title = {Scheitels\"atze f\"ur Regelfl\"achen.}, journal = {Manuscripta mathematica}, volume = {4}, year = {1971}, pages = {309-322}, zbl = {0223.53010}, url = {http://dml.mathdoc.fr/item/GDZPPN002216388} }
Hoschek, Josef. Scheitelsätze für Regelflächen.. Manuscripta mathematica, Tome 4 (1971) pp. 309-322. http://gdmltest.u-ga.fr/item/GDZPPN002216388/