1. J. Hilnor, in: “Relativity, Groups and Topology II”, B. De Witt and R. Stora, North Holland, Amsterdam (1984).
2. R. G. Yates, Comm. Math. Phys. 76: 255, (1980).
3. S. Deser and B. Zumino, Phys. Lett. 62B: 335, (1976).
4. D. Freedman, P. van Nieuwenhuizen, and S. Ferrara, Phys. Rev. D13: 3214 (1976).
5. E. Cartan, “Leçons sur la théorie des spineurs”, Hermann, Paris (1938).