1. A. De Rújula, H. Georgi andS. L. Glashow:Phys. Rev. D,12, 147 (1975).
2. C. N. Yang andR. Mills:Phys. Rev.,96, 191 (1954).
3. E. S. Abers andB. W. Lee:Phys. Report,9 C, 1 (1973).
4. W. Marciano andH. Pagels:Phys. Rev. 36 C, 137 (1978).
5. L. B. Okun:New particles and quarks, Lectures delivered atThe Eighth Session of Spring School of Experimental and Theoretical Physics, Part I,Yerevan, April 8–19, 1975 (Yerevan, 1975), p. 8.