Reprinted in Selected papers of Abdus Salam, editor A. Ali et al., p. 204-209..
Gauge theory of weak and electromagnetic interactions, eidtor C. H. Lai, p. 113-123.
Some proofs are presented of Goldstone's conjecture, that if there is continuous symmetry transformation under which the Lagrangian is invariant, then either the vacuum state is also invariant under the transformation, or there must exist spinless particles of zero mass.
Related references More (earlier) information appears in J. Goldstone, Nuovo Cim. 19 (1961) 154;
Analyse data from H. Lehmann, Nuovo Cim. 11 (1954) 342;
A. Salam and J. C. Ward, Phys. Rev. Lett. 5 (1960) 512;
Y. Nambu and G. Jona-Lasinio, Phys. Rev. 122 (1961) 345;
W. Heisenberg, Zeit. Naturforschung 14 (1959) 441;
ex, qn, mass
Perturbative and general proofs of the Goldstone theorem.