Uniqueness of symplectic canonical class, surface cone and symplectic   cone of 4-manifolds with b^+=1
  Let M be a closed oriented smooth 4-manifold admitting symplectic structures. If M is minimal and has b^+=1, we prove that there is a unique symplectic canonical class up to sign, and any real second cohomology class of positive square is represented by symplectic forms. Similar results hold when M is not minimal. 
Tian-Jun Li, Ai-Ko Liu