1. See talks in these Proceedings.
2. Yu. Gol’fand and E. Lichtman, JETP Letters
13 (1971) 323.
3. D. Volkov and V. Akulov, JETP Letters
16 (1972) 438. Phys. Lett. 46B (1973) 109.
4. V. Akulov and D. Volkov, Theor. Math. Phys. 18 (1974) 28.
5. J. Wess and B. Zumino, Nucl. Phys. B70 (1974) 39.