Iranian Mathematical Society (IMS) Bulletin of the Iranian Mathematical Society 1017-060X 35 No. 2 2011 01 16 An Operator Extension of Bohr's inequality77 84 en M. S. Moslehian Ferdowsi University of Mashhad J. E. Pecaric University of Zagreb I. Peric University of Zagreb 2011 01 16 Bohr’s inequality operator norm operator inequality positive operator Hilbert space