Front matter

Conventions: ambient $M={\mathbb{R}}^4$, $\eta =\mathrm{diag}(1,-1,-1,-1)$, $\mathcal{P}r=r-\frac{1}{2}\eta {\mathrm{tr}}_{\eta }r$, Gram $G=\mathrm{diag}(1,-2,-2,-2,$$1,2,2,1,2,1)$, dual basis $B^i=(G^{-1}{)}^{ii}{B}_i$; Hessian on field directions $B_i$; propagator/source contraction on dual slots $-\mathcal{P}{B}^i$. The XI inverse ${G_{\mathrm{gr}}}^{\mathrm{R}}=-\mathcal{P}{E_0}^{\mathrm{R}}$ is not equated with the X-sheet ${{\Delta }_R}^{\mathrm{gr}}=-4\mathcal{P}{E_0}^{\mathrm{R}}$. Series voice: Constructed / Proved obstructed / Unresolved / Non-claims. Predecessor quotations are exact.