@article{AM2_1977__15_136663,
     author = {Walter Benz},
     title = {The functional equation of distance preservance in spaces over rings. {(Short} {Communication).}},
     journal = {Aequationes mathematicae},
     pages = {308--308},
     year = {1977},
     volume = {15},
     zbl = {0368.39003},
     url = {http://geodesic.mathdoc.fr/item/AM2_1977__15_136663/}
}