Duality Transformations in the Ten-Dimensional Action and New   Superstring Theories
  Type II superstring theory with mixed Dirichlet and Neumann boundary conditions admit antisymmetric tensors with varying degrees in the spectrum. We show that there exists a family of dual supergravity lagrangians to the $N=2$ type IIA action in ten dimensions. The duality transformations and the resulting actions are constructed explicitely. 
A. H. Chamseddine (ETH)