1. J.E. Bowcock, W. N. Cottingham andP.H. Gn: in preparation.
2. See, for example,Pion-Nucleon Scattering, edited byG. Shaw andD. Y. Wong (New York, 1970), p. 20.
3. V. Singh:Phys. Rev.,129, 1889 (1963).
4. A. Martin:Nuovo Cimento,59A 131 (1969).
5. SeePion-Nucleon Scattering, edited byG. Shaw andD.Y. Wong (New York, 1970), p. 27.