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2. A. Pevsner, D. M. Ritson andM. Widgoff: private communication. We are grateful to these authors for making their data available to us.
3. J. P. Astburt, A. Bonetti, M. Ceccarelli, N. Dallaporta, C. Franzinetti, M. Friedlander andG. Tomasini:Suppl. Nuovo Gimento,12, 448 (1954).
4. E. Amaldi, E. Fabri, T. F. Hoang, W. O. Lock, L. Scarsi, B. Touschek andB. Vitale:Suppl. Nuovo Gimento,12, 419 (1954).
5. W. H. Barkas andD. M. Young: UCRL-2579 (revised), unpublished.