Characterising subspaces of Banach spaces with a Schauder basis having   the shift property
  We give an intrinsic characterisation of the separable reflexive Banach spaces that embed into separable reflexive spaces with an unconditional basis all of whose normalised block sequences with the same growth rate are equivalent. This uses methods of E. Odell and T. Schlumprecht. 
Christian Rosendal
math.FA