@article{AM2_1979__19_136811,
     author = {Eberhard M. Schr\"oder},
     title = {Eine {Erg\"anzung} zum {Satz} von {Beckman} und {Quarles.}},
     journal = {Aequationes mathematicae},
     pages = {89--92},
     publisher = {mathdoc},
     volume = {19},
     year = {1979},
     zbl = {0413.51002},
     url = {http://geodesic.mathdoc.fr/item/AM2_1979__19_136811/}
}