• Bulletin of the Korean Mathematical Society
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• v.49 no.6
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• pp.1275-1289
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• 2012

In this manuscript we solve in the positive a question informally proposed by Enflo on the measure of the set of isometric reflection vectors in non-Hilbert 2-dimensional real Banach spaces. We also reformulate equivalently the separable quotient problem in terms of isometric reflection vectors. Finally, we give a new and easy example of a real Banach space whose dual has a non-trivial L-summand that does not come from an M-ideal in the predual.