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3. Daniel, R. R., Davies, J. H., Mulvey, J. H. and Perkins, D. H.Bristol Conference on V-Particles and Heavy Mesons December, 1951).
4. George, E. P. ..Progress in Cosmic Ray Physics, Ch. VII, p. 395, Ed. by J. G. Wilson (North Holland Pub. Co., 1952).
5. Greisen, K. I...Phys. Rev., 1948,73, 521.