1. Schwarz, J.H., ed. “Superstrings: the first fifteen years” (World Scientific, 1985 ).
2. Cremmer, E., Julia, B. and Scherk, J. Phys. Lett. 76B, 409 (1978).
3. Duff, M.J., Pope, C.N. and Nilsson, B.E.W., Physics Reports 130, 1 (1986).
4. Chamseddine, A., Phys. Rev. 1724, 3065 (1981).
5. Gates, S.J. and Nishino, H., Phys. Lett. 157B, 157 (1985).