... spaces has been recently studied byAlsina 44, M irmostafaee and Moslehian 45 and Mirzavaziri and Moslehian 40,Mihet¸ and Radu 46,Mihet¸etal.47, 48, Baktash et al. 49, and Saadati ... Functional EquationReza Saadati, M. M. Zoh di, and S. M. VaezpourDepartment of Mathematics, Science and Research Branch, Islamic Azad University, Ashrafi Esfahani Ave,Tehran 14778, IranCorrespondence ... Journal of MathematicalAnalysis and Applications, vol. 251, no. 1, pp. 264–284, 2000.21 Th. M. Rassias, “On the stability of functional equations and a problem of Ulam,” Acta ApplicandaeMathematicae,...