  We present definitions and formulas that may be useful for a consistent
computation of helicity amplitudes for the process gamma* N -> N* in
theoretical approaches. Of particular importance is the correct determination
of the common sign of the amplitudes and of the relative sign between the
transverse (A12,A32) and longitudinal (S12) amplitudes. This clarification is
necessary to clear up confusions present in theoretical works. Using the
definitions presented in this paper will enable a direct comparison with
amplitudes extracted from experimental data.
