@article{AM2_1985__28_137072,
     author = {Wolfgang Sander},
     title = {On a sum form functional equation.},
     journal = {Aequationes mathematicae},
     pages = {321--326},
     publisher = {mathdoc},
     volume = {28},
     year = {1985},
     zbl = {0576.39010},
     url = {http://geodesic.mathdoc.fr/item/AM2_1985__28_137072/}
}