@article{AM2_1993__45_2-3_137530,
     author = {Claus Hammer},
     title = {\"Uber die {Funktionalungleichung} f(x +y) + f(xy) ... f(x) + f(y) + f(x)f(y).},
     journal = {Aequationes mathematicae},
     pages = {297--299},
     publisher = {mathdoc},
     volume = {45},
     number = {2-3},
     year = {1993},
     zbl = {0788.39007},
     url = {http://geodesic.mathdoc.fr/item/AM2_1993__45_2-3_137530/}
}