  We consider the Hubbard model and its extensions on bipartite lattices. We
define a dynamical group based on the $\eta$-pairing operators introduced by
C.N.Yang, and define coherent pairing states, which are combinations of
eigenfunctions of $\eta$-operators. These states permit exact calculations of
numerous physical properties of the system, including energy, various
fluctuations and correlation functions, including pairing ODLRO to all orders.
This approach is complementary to BCS, in that these are superconducting
coherent states associated with the exact model, although they are not
eigenstates of the Hamiltonian.
