1. M. Goldberger andS. B. Treiman:Phys. Rev.,10, 1178 (1958).
2. N. Barash-Schmidt, G. Conforto, A. Barbaro-Galtieri, M. Ross, A. H. Rosenfeld, P. Söding andC. G. Wohl:Review of particle properties, UCRL-8030, Jan. 1969.
3. See for instanceS. Gasiorowicz:Elementary Particle Physics (New York, 1966), p. 583.
4. See for instanceN. Cabibbo:Rapporteur's talk at the XIII International Conference on High-Energy Physics.
5. The number 1.28 forf A K /f A π quoted from ref. (4) See for instanceN. Cabibbo:Rapporteur's talk at the XIII International Conference on High-Energy Physics. is obtained by assuming that the vector currents are not renormalized.