1. T. Banks, Santa Cruz preprint SCIPP-88/09
2. S. Coleman, Harvard preprints HUTP-88/A08, HUTP-88A022
3. S. Giddings and A. Strominger, Harvard preprint HUTP-88/A036
4. Wormholes and the cosmological constant;Banks;SLAC preprint,1988
5. M. Wise and B. Grinstein, Caltech preprint CALT-68-1505