Form factors in the finite volume

We study exactly solvable models of quantum statistical mechanics. Our main example is the Quantum nonlinear Schrodinger equation. This model can be s olved by algebraic Bethe Ansatz. We are interested in the expression for a form factor of the local field in the finite volume F-N = [0\ Pi(j=1)(N) C( mu(j))phi(0, 0) Pi(j=1)(N+1) B(lambda(j))\0].We think that this is the univ ersal feature: finite representation for this form factor. We think that th is is the universal feature: finite volume form factor of any exactly solva ble model can be represented a determinant.