Classification of Extensions of Classifiable C*-algebras
  We classify extensions of certain classifiable C*-algebras using the six term exact sequence in K-theory together with the positive cone of the K_0-groups of the distinguished ideal and quotient. We then apply our results to a class of C*-algebras arising from substitutional shift spaces. 
Soren Eilers, Gunnar Restorff, Efren Ruiz