Tsirelson-like spaces and complexity of classes of Banach spaces
  Employing a construction of Tsirelson-like spaces due to Argyros and Deliyanni, we show that the class of all Banach spaces which are isomorphic to a subspace of $c_{0}$ is a complete analytic set with respect to the Effros Borel structure of separable Banach spaces. Moreover, the classes of all separable spaces with the Schur property and of all separable spaces with the Dunford-Pettis property are $\mathbf{\Pi}^{1}_{2}$-complete. 
Ond\v{r}ej Kurka
math.FA