1. N. Arkani-Hamed, S. Dimopoulos, G. Dvali, hep-ph/9803315, to appear in Phys. Lett. B.
2. I. Antoniadis, N. Arkani-Hamed, S. Dimopoulos, G. Dvali, hep-ph/9804398, to appear in Phys. Lett. B.
3. N. Arkani-Hamed, S. Dimopoulos, G. Dvali, hep-ph/9807344.
4. See for example: J. Polchinski, TASI lectures on D-branes, hep-th/9611050.
5. A possible new dimension at a few TeV