Topological versus Non--Topological Theories and $p-q$ Duality in $c \le   1$ 2d Gravity Models
  We discuss the non--perturbative formulation for $c \leq 1$ string theory. The field theory like formulation of topological and non--topological models is presented. The integral representation for arbitrary $(p,q)$ solutions is derived which explicitly obeys $p-q$ duality of these theories. The exact solutions to string equation and various examples are also discussed. 
S.Kharchev, A.Marshakov