Stability of functional equations of Drygas in the space of Schwartz distributions

In this paper we reformulate and prove the stability theorems of S.M. Jung and P.K. Sahoo [S.M. Jung, P.K. Sahoo, Stability of a functional equation of Drygas, Aequationes Math. 64 (2002) 263–273] in the spaces of generalized functions such as the Schwartz distributions and tempered distributions.