1. R. Brown et al., Nature (London), 163 (1949) 82.
2. CF. Powell, A discussion on V-particles and heavy mesons, Proc. R. Soc. Lond. A, 253 (1954) 278.
3. R.W. Thompson et al., in Proc. Congres Int. sur le Rayonnement Cosmique, Bagneres de Bigorre (Univ. Toulouse, 1953), p. 30.
4. Particle Data Group, Phys. Rev. D50 (1994) 1173.
5. G.D. Rochester, in “Pions to Quarks” (ed. L.M. Brown, M. Dresden, L. Hoddeson) pp. 57–88. Cambridge (U.K.): C.U.P. (1989).