@article{AM2_1991__42_3_137420,
     author = {Peter Semrl},
     title = {On ring derivations and quadratic functionals.},
     journal = {Aequationes mathematicae},
     pages = {80--84},
     publisher = {mathdoc},
     volume = {42},
     number = {3},
     year = {1991},
     zbl = {0764.46054},
     url = {http://geodesic.mathdoc.fr/item/AM2_1991__42_3_137420/}
}