@article{ELMA_1980__35_141239,
     author = {J. T\"olke},
     title = {Parabeln mit gemeinsamen isotropem {Kr\"ummungskreis.}},
     journal = {Elemente der Mathematik},
     pages = {14--17},
     publisher = {mathdoc},
     volume = {35},
     year = {1980},
     zbl = {0425.53005},
     url = {http://geodesic.mathdoc.fr/item/ELMA_1980__35_141239/}
}