From N=2 Supergravity to Constrained Moduli Spaces
  In this talk we review some results concerning a mechanism for reducing the moduli space of a topological field theory to a proper submanifold of the ordinary moduli space. Such mechanism is explicitly realized in the example of constrained topological gravity, obtained by topologically twisting the N=2 Liouville theory. 
D.Anselmi, P.Fre', L.Girardello and P.Soriani