Rees algebras and polyhedral cones of ideals of vertex covers of perfect   graphs
  Let G be a perfect graph and let J be its ideal of vertex covers. We show that the Rees algebra of J is normal and that this algebra is Gorenstein if G is unmixed. Then we give a description--in terms of cliques--of the symbolic Rees algebra and the Simis cone of the edge ideal of G. 
Rafael H. Villarreal