1. See for example: M. K. Gaillard, lecture presented at the 1978 SLAC Summer Institute
2. G. Trilling: invited talk at the 1980 Madison Conference
3. T. Hayashi et al.: Prog. Theor. Phys.49, 351 (1973);52, 636 (1974); S. P. Rosen: Phys. Rev. Lett.44, 4 (1980); I. Bigi, L. Stodolsky: SLAC Pub. 2410 (1979); M. Matsuda, M. Nakagawa, S. Ogawa: Nagoya preprint (1979); E. Ma, S. Pakvasa, W. A. Simmons: Z. Phys. C ? Particles and Fields5, 309 (1980)
4. M. Bander, D. Silvermann, A. Soni: Phys. Rev. Lett.44, 7 (1980); I. I. Bigi: Z. Phys. C ? Particles and Fields5, 313 (1980); V. Barger, J. P. Leveille, P. M. Stevenson; Phys. Rev. D22, 693 (1980)
5. W. Bernreuther, O. Nachtmann, B. Stech: Z. Phys. C ? Particles and Fields4, 257 (1980); H. Fritzsch, P. Minkowski: Phys. Lett.90 B, 455 (1980)