1. See, for instance,G. Veneziano:Narrow-resonance models compatible with duality and their developments, inLectures at the International School of Subnuclear Physics, Erice, Sicily (1970).
2. See, for instance,R. G. Newton:The Complex J-Plane (New York, 1964).
3. H. Fleming andA. Montes Filho:Nuovo Cimento,14 A, 215 (1973);D. Sivers:Phys. Rev. D,3, 2275 (1971).
4. V. N. Gribov:Sov. Phys. JETP,16, 1080 (1963).
5. See ref. (3).