@article{AM2_1992__43_1_137461,
     author = {Peter Semrl and Damijan Kobal},
     title = {Generalized {Cauchy} functional equation and characterizations of inner product spaces.},
     journal = {Aequationes mathematicae},
     pages = {183--190},
     publisher = {mathdoc},
     volume = {43},
     number = {1},
     year = {1992},
     zbl = {0755.39007},
     url = {http://geodesic.mathdoc.fr/item/AM2_1992__43_1_137461/}
}