@article{MZ_1978__159_172647,
     author = {Paul E. Ehrlich and Hans-Christoph Im Hof},
     title = {Metric {Circles} and {Bisectors.}},
     journal = {Mathematische Zeitschrift},
     pages = {101--106},
     publisher = {mathdoc},
     volume = {159},
     year = {1978},
     zbl = {0354.53037},
     url = {http://geodesic.mathdoc.fr/item/MZ_1978__159_172647/}
}