@article{AM2_1982__25_136946,
     author = {A. J\'arai},
     title = {Regularity properties of functional equations.},
     journal = {Aequationes mathematicae},
     pages = {52--66},
     publisher = {mathdoc},
     volume = {25},
     year = {1982},
     zbl = {0517.39009},
     url = {http://geodesic.mathdoc.fr/item/AM2_1982__25_136946/}
}