1. For recent reviews see: J.H. Schwarz, Lectures on superstring and M theory dualities, hep-th/9607201;
2. A. Sen, Unification of string dualities, hep-th/9609176;
3. M.R. Douglas Superstring dualities, Dirichlet branes and the small scale structure of space, hep-th/9610041.
4. J. Polchinski, S. Chaudhuri and C.V. Johnson, Notes on D-branes, hep-th/9602052;
5. J. Polchinski, TASI lectures on D-branes, hep-th/9611050.