@article{03734456, title = {Generalization of sum representation functional equations. I.}, journal = {International Journal of Mathematics and Mathematical Sciences}, volume = {2}, year = {1979}, pages = {459-471}, doi = {10.1155/S0161171279000351}, zbl = {0468.39006}, language = {en}, url = {http://dml.mathdoc.fr/item/03734456} }
Kannappan, P.L.; Sathyabhama, V. Generalization of sum representation functional equations. I.. International Journal of Mathematics and Mathematical Sciences, Tome 2 (1979) pp. 459-471. doi : 10.1155/S0161171279000351. http://gdmltest.u-ga.fr/item/03734456/