It is well-known that the concept of Hyers-Ulam-Rassias stability
originated by Th. M. Rassias (Proc. Amer. Math. Soc. 72(1978),
297-300) and the concept of Ulam-Gavruta-Rassias stability by J.
M. Rassias (J. Funct. Anal. U.S.A. 46(1982), 126-130; Bull. Sc.
Math. 108 (1984), 445-446; J. Approx. Th. 57 (1989), 268-273) and P.
Gavruta (``An answer to a question of John M. Rassias concerning
the stability of Cauchy equation", in: Advances in Equations and
Inequalities, in: Hadronic Math. Ser. (1999), 67-71). In this
paper we give results concerning these two stabilities.