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Published online by Cambridge University Press: 20 November 2018
Let ${{B}_{Y}}$ denote the unit ball of a normed linear space
$Y$. A symmetric, bounded, closed, convex set
$A$ in a finite dimensional normed linear space
$X$ is called a sufficient enlargement for
$X$ if, for an arbitrary isometric embedding of
$X$ into a Banach space
$Y$, there exists a linear projection
$P:\,Y\,\to \,X$ such that
$P({{B}_{Y}})\,\subset \,A$. Each finite dimensional normed space has a minimal-volume sufficient enlargement that is a parallelepiped; some spaces have “exotic” minimal-volume sufficient enlargements. The main result of the paper is a characterization of spaces having “exotic” minimal-volume sufficient enlargements in terms of Auerbach bases.