1. A. Trautman, Preprint no. 47 Dep. of Theor. Phys. N. Copernicus University, Cracow, Poland, 1968.
2. R. Hermann, Phys. Rev.,177, 2449, 1969.
3. R. Hermann, Vector Bundles in Mathematical Physics, Vol. I, W. A. Benjamin, New York, 1970, pp. 184–90.
4. M. Daniel etC. M. Viallet, Rev. of Mod. Phys.,52, 175, 1980.
5. J. D. Bjorken etS. D. Drell, Relativistic Quantum Fields, Mc. Graw-Hill Book Company, New York, 1965, chap. 11.