complete by building Lorentz tensors from combinations of elements of the set $\{ \eta^{\mu\nu}, p^\mu, 
q^\mu, \Gamma_{(n)}^{\mu_1 \ldots \mu_n} \}$. These have, of course, to be consistent with the symmetries of the Lorentz indices of the operator inserted in the Green’s function. From this it is clear that our basis is complete for each operator, as there is no room to build additional tensors from the basic structures of the Lorentz and spinor vector spaces.

Given that there is more than one amplitude for each operator insertion, we have to be careful in defining the renormalization constant in the RI${}^\prime$/SMOM scheme. For all the cases we consider here the ultraviolet divergence resides in a subset of the amplitudes which in fact contains at least one element except for the special case of the vector current. For $V$ the RI${}^\prime$/SMOM scheme renormalization has to be treated separately. If, for the moment, we denote this representative basis tensor by the label $0$ then we define the renormalization constant for the operator ${\cal O}$, $Z^{\mbox{\footnotesize{RI$^\prime$/SMOM}}}_{\cal O}$, by the condition $$\left. \lim_{\epsilon\rightarrow 0} \left[ 
Z^{\mbox{\footnotesize{RI$^\prime$}}}_\psi 
Z^{\mbox{\footnotesize{RI$^\prime$/SMOM}}}_{\cal O} \Sigma^{\cal O}_{(0)}(p,q) 
\right] \right|_{p^2 \, = \, q^2 \, = \, - \mu^2} ~=~ 1 
\label{rissmomdef}$$ where 