1. S. Drell:Proceedings of the 1958 Annual International Conference on High Energy Physics at CERN (edited byB. Ferretti, Geneva, 1958), p. 32;S. Drell andF. Zacharlasen:Phys. Rev.,111, 1727 (1958).M. Sugawara (preprint received May, 1960) has recently suggested that the forward pion-nucleon scattering dispersion relations may also be valid without subtractions.
2. J. Orear:Phys. Rev.,96, 176 (1954).
3. J. Hamilton andW. S. Woolcock:Phys. Rev.,118, 291 (1960).
4. H. P. Noyes andD. N. Edwards (UCRL report No. 5771-T, November, 1959) have given the most complete evaluation off 2 from the pion-nucleon scattering data to date.
5. M. J. Longo, J. A. Helland, W. N. Hess, B. J. Moyer andV. Perez-Mendez:Phys. Rev. Lett.,3, 568 (1959) and the references given therein.