1. Functional Equations in Several Variables;Aczél,1989
2. J.-H. Bae, On the Ulam stability problem of a quadratic functional equation, Korean J. Comput. and Appl. Math, to appear.
3. On a general Hyers–Ulam-stability result;Borelli;Internat. J. Math. Math. Sci.,1995
4. Remarks on the stability of functional equations;Cholewa;Aequationes Math.,1984
5. On the stability of the quadratic mapping in normed spaces;Czerwik;Abh. Math. Sem. Univ. Hamburg,1992