@article{GDZPPN002038412, title = {A new Pythagorean functional equation.}, journal = {Aequationes mathematicae}, volume = {40}, year = {1990}, pages = {271-280}, zbl = {0722.30012}, url = {http://dml.mathdoc.fr/item/GDZPPN002038412} }
Haruki, H. A new Pythagorean functional equation.. Aequationes mathematicae, Tome 40 (1990) pp. 271-280. http://gdmltest.u-ga.fr/item/GDZPPN002038412/