@article {67182,
	title = {Characterization of the class of unitary operators by operator inequalities},
	journal = {Linear and Multilinear algebraLinear and Multilinear Algebra},
	volume = {59},
	year = {2011},
	month = {2011},
	pages = {1069-1074},
	isbn = {0308-1087},
	author = {Seddik, Ameur}
}
