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"Lees involvement with gauge theories dated back to 1964. He was concerned about the fact that superconductors appear to provide a counterexample to the general theorem, which requires that spontaneous symmetry breaking is always accompanied with massless spin-zero bosons. With Klein, he wrote an article suggesting that the same might occur in relativistic theories. It was soon realized that this is indeed the case, provided the broken symmetry is a gauge symmetry, as it is in a superconductor."






