Iranian Mathematical Society (IMS) Bulletin of the Iranian Mathematical Society 1017-060X 37 No. 3 2011 09 15 A characterization of L-dual frames and L-dual Riesz bases21 32 en A. Ahmadi A. Askari Hemmat 2009 11 06 Hyers-Ulam-Rassias stability generalized derivation bounded central approximate identity faithful Banach algebra