1. L. Van Hove: Rapporteur's talk,XIII International Conference on High Energy Physics, Berkeley, 1966.G. Höhler,et al.: Karlsruhe preprint (1967).M. N. Focassi andG. Giacomelli: CERN report 66-18 (1966).
2. S. Kormanyos, A. D. Krisch, J. R. O'Fallon, K. Kuddick andL. G. Ratner:Phys. Rev. Lett.,16, 709 (1966); and contribution to the 1967Heidelberg Conference.
3. A complete list of the data analysed between 2 and 6 GeV/c is given Appendix C. Some other data are listed below.E. H. Bellamy, T. F. Buckley, W. Busza, D. G. Davis, B. G. Duff, F. F. Heymann, P. V. March, C. C. Nimmon, A. Stafanini, J. A. Strong, R. N. F. Walker andD. T. Walton:Proc. Roy. Soc., A289, 509 (1966); and report RPP/H/21 University College London (1966);L. D. Jacobs: Thesis, report UCRL-16877 (1966);A. V. Stirling, P. Sonderegger, J. Kirz, P. Falk-Vairant, O. Guisan, C. Bruneton, P. Borgeaud, M. Yvert, J. P. Guillaud, C. Caversasio andB. Amblard:Phys. Rev. Lett.,14, 763 (1965);20, 75 (1966);I. Mandelli, A. Bigi, R. Carrara, M. Whalig andL. Sodickson:Phys. Rev. Lett.,14, 408 (1965).
4. G. Höhler andJ. Giesecke:Phys. Lett.,12, 149 (1964);R. M. Heinz andM. H. Ross:Phys. Rev. Lett.,14, 1091 (1965);A. S. Carroll, J. F. Corbett, C. J. S. Damerell, N. Middlemas, D. Newton, A. B. Clegg andW. S. C. Williams:Phys. Rev. Lett.,16, 288 (1966);17, 1274 (1966);R. K. Logan andL. Sertorio:Phys. Rev. Lett.,17, 834 (1966);R. J. N. Phillips:Nuovo Cimento,45A, 245 (1966);P. Grannis, H. Steiner andL. Valentin: UCRL report 16750 (1966);J. Baacke andM. Yvert: Report submitted to theXIII International Conference on High Energy Physics, Berkeley, 1966;B. R. Desai, D. T. Gregorich andR. Ramachandran:Phys. Rev. Lett.,18, 565 (1967);G. Altarelli, A. Borgese, F. Buccella andM. Colloci:Nuovo Cimento,48 A, 245 (1967);A. Yokosawa:Phys. Rev.,159, 1431 (1967);J. Dreitlein andK. Mahanthappa:Nuovo Cimento,48 A, 275 (1967);R. Dolen, D. Horn andC. Schmid: CALT-68-143 (1967), submitted toPhys. Rev. See also ref. (6). Also many others.
5. Our argument presented in Subsect.3 2 is similar to that given by:R. Dolen, D. Horn andC. Schmid: CALT-68-143 (1967), submitted toPhys. Rev. (see Appendix B); For the dispersion relation on the (−) amplitude see also:M. Restignoli, L. Sertorio andM. Toller:Phys. Rev.,150, 1389 (1966);