1. Wilson, K., Zimmermann, W.: NYU Preprint 1971.
2. Streater, R., Wightman, A.: PCT, spin and statistics. New York: Benjamin 1964.
3. See, for instance, Ref. (2).
4. Jost, R., Lehmann, H.: Nuovo Cimento5, 1598 (1957).
5. Dyson, F.: Phys. Rev.110, 1460 (1958).