1. A. I. Alihanian et al.: International Conference on High Energy Physics (Moscow, May 1956);A. I. Alihanian, N. V. Šostakovič, A. T. Dadaian, V. N. Fedorov andB. N. Deriagin:Žurn. Ėxp. Theor. Phyz.,4, 817 (1957), also for previous references.
2. J. Orear, E. Bierman andS. Rosendarff: Postdeadline paper for the 1958 New York Meeting of theAm. Phys. Soc.
3. J. W. Keuffel, R. L. Call andW. H. Sandmann:Bull. Am. Phys. Soc.,3, 162 (1958).
4. A few days ago other results have been reported, together with those contained in this letter, at the C.E.R.N. Conference (Geneva, July 1958), in the general report on strange particles byJ. Steinberger.
5. E. Fiorini, R. Giacconi andC. Succi:Nuovo Cimento,6, 943 (1957).