1. Fisher, J.C., private communication.
2. Thouless, D.J., to be published.
3. Brueckner, K.A., Soda, T., Anderson, P.W. and Morel, P., Phys. Rev. (to be published).
4. Emery, V.J. and Sessler, A.M., Phys. Rev. (to be published).
5. Theory of Superconductivity