1. J. Ellis: lectures presented at the1976 Les Houches, Summer School on A Weak and Electromagnetic Interaction at High Energies, edited byR. Balian andCh. Llewellyn Smith (Amsterdam, 1977), p. 1.
2. J. Ellis andC. T. Sachrajda:Proceedings of the Cargèse Summer School on Quarks and Leptons, July 9–28, 1979, CERN preprint TH. 2782 (1979).
3. G. P. Lepage andS. J. Brodsky:Phys. Rev. D,22, 2157 (1980).
4. A. De Rújula andF. Martin: preprint MIT-CTP-851 (1980).
5. R. N. Faustov:Ann. Phys. (N. Y.),78, 176 (1973).