@article{ELMA_1957__12_140666,
     author = {E. Trost},
     title = {Eine charakteristische {Eigenschaft} der {Rotationsfl\"achen} zweiten {Grades.}},
     journal = {Elemente der Mathematik},
     pages = {73--75},
     publisher = {mathdoc},
     volume = {12},
     year = {1957},
     zbl = {0081.15602},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1957__12_140666/}
}