@article{AM2_1977__16_136702,
     author = {Walter Benz},
     title = {The functional equation of distance preservance in spaces over rings.},
     journal = {Aequationes mathematicae},
     pages = {303--308},
     publisher = {mathdoc},
     volume = {16},
     year = {1977},
     zbl = {0368.39003},
     url = {http://geodesic.mathdoc.fr/item/AM2_1977__16_136702/}
}