1. J. A. Newth:Suppl. Nuovo Cimento,11, 297 (1954).
2. Most of these were selected before the criteria given in Section1 were established. Some of the 50 were later rejected for various reasons. An analysis of the remaining interactions is being made (2).
3. L. Montanet: to be published.
4. C. Franzinetti andG. Morpurgo:Suppl. Nuovo Cimento,6, 469 (1957).
5. Article byD. H. Perkins inProgress in Elementary Particle and Cosmic-Ray Physics, vol.5 (Amsterdam).