Gravitpn-graviton scattering, Bel-Robinson and energy (pseudo)-tensors

Motivated by recent work involving the graviton-graviton tree scattering am plitude, and its twin descriptions as the square of the Bel-Robinson tensor , B-mu nu alpha beta, and as the 'current-current interaction' square of gr avitational energy pseudo-tensors t(alpha beta), we find an exact tensor-sq uare root equality B-mu nu alpha beta = partial derivative(mu nu)(2)t(alpha beta), for a combination of Einstein and Landau-Lifschitz t(alpha beta), i n Riemann normal coordinates. In the process, we relate, on-shelf, the usua l superpotential basis for classifying pseudo-tensors with one spanned by p olynomials in the curvature.