... dyshin@uos.ac.kr4Department of Mathematics,University of Seoul, Seoul 130-743,Republic of KoreaFull list of author information isavailable at the end of the articleAbstractIn this paper, we prove the Hyers-Ulam ... Mathematics,University of Ulsan, Ulsan 680-749, Republic of Korea3Department of Mathematics, Daejin University, Kyeonggi 487-711, Republic of Korea4Department of Mathematics, University of Seoul, Seoul ... visiting the research Institute of Mathematics, Seoul National University.Author details1Department of Mathematics, Hanyang University, Seoul 133-791, Republic of Korea2Department of Mathematics,University...