  Motivated by recent work involving the graviton-graviton tree scattering
amplitude, and its twin descriptions as the square of the Bel-Robinson tensor,
$B_{\m\n\a\b}$, and as the "current-current interaction" square of
gravitational energy pseudo-tensors $t_{\a\b}$,we find an exact tensor-square
root equality $B_{\mn\a\b} = \pa^2_\mn t_{\a\b}$, for a combination of Einstein
and Landau-Lifschitz $t_\ab$, in Riemann normal coordinates. In the process, we
relate, on-shell, the usual superpotential basis for classifying pseudo-tensors
with one spanned by polynomials in the curvature.
