1. V. V. Anisovitch:Sov. Phys. JETP,17, 1072 (1963);R. F. Peierls andJ. Tarski:Phys. Rev.,129, 981 (1963).
2. N. N. Khuri andS. B. Treiman:Phys. Rev.,119, 1115 (1960);J. B. Bronzan andC. Kacser:Phys. Rev.,132, 2703 (1963);G. Bonnevay:Nuovo Cimento,30, 1325 (1963);I. J. R. Aitchison:Nuovo Cimento,35, 434 (1965) contains a review.
3. P. V. Landshoff andD. I. Olive:Journ. Math. Phys., to be published (1966).
4. P. V. Landshoff:The S-matrix without field theory, D.A.M.T.P. preprint (1963)R. J. Eden, P. V. Landshoff, D. I. Olive andJ. C. Polkinghorne:The Analytic S-Matrix (Cambridge, 1966).
5. J. G. Cordes: D.A.M.T.P. preprint (1966).