Using electric current conservation, it is shown that in the series expansion of the amplitudes of radiative decays (with two particles at most in the final state, apart from the photon) in powers of the photon fourmomentum, terms of order zero vanish unless they belong to photon pole diagrams.

• Received 10 February 1967

DOI:https://doi.org/10.1103/PhysRev.160.1555