@article{GDZPPN002219646, title = {\"Uber die Funktionalgleichung f(f(x) * f(y)) = f(x*y).}, journal = {Manuscripta mathematica}, volume = {18}, year = {1976}, pages = {371-390}, zbl = {0335.39005}, url = {http://dml.mathdoc.fr/item/GDZPPN002219646} }
Spilker, Jürgen; Dhombres, Jean. Über die Funktionalgleichung f(f(x) * f(y)) = f(x*y).. Manuscripta mathematica, Tome 18 (1976) pp. 371-390. http://gdmltest.u-ga.fr/item/GDZPPN002219646/