  Numerical results are presented for a generalized resonance valence bond
state which includes both ionic and covalent contributions in each bond ; non
nearest-neighbor bonds are also considered. Variational calculations have been
performed and the space group symmetry has been taken into account. The results
for the Hubbard Hamiltonian are compared with the exact ones for the $ 2 X 2 X
2 $ and the $ 4 X 4 $ lattices. The agreement is quite satisfactory for large
values of the interaction U ( for U=40 the overlap with the exact ground state
wave function is 0.999 ). Several correlation functions are also compared.
