@article{AM2_1985__29_137087,
     author = {Wolfgang Sander},
     title = {About solutions of a functional equation.},
     journal = {Aequationes mathematicae},
     pages = {135--144},
     publisher = {mathdoc},
     volume = {29},
     year = {1985},
     zbl = {0588.39007},
     url = {http://geodesic.mathdoc.fr/item/AM2_1985__29_137087/}
}