Approximate additive and quadratic mappings in ۲-Banach spaces and related topics

Department of Mathematics Education and the RINS, Gyeongsang National University, Chinju ۶۶۰-۷۰۱, Korea

Research Institute for Natural Sciences, Hanyang University, Seoul ۱۳۳-۷۹۱, Korea

Department of Mathematics, Semnan University, P. O. Box ۳۵۱۹۵-۳۶۳, Semnan, Iran.