  We study the inclusive two jet triply differential cross section
$d^3\sigma/dE_Td\eta_1d\eta_2$ at Fermilab energies. Different $\eta_1$ and
$\eta_2$ pseudorapidity regions are directly related to both the parton level
matrix elements and the parton densities at leading order. We present the
next-to-leading order [${\cal O}(\alpha_s^3)$] corrections and show that the
shape of the distribution at fixed transverse energy $E_T$ is a particularly
powerful tool for constraining the parton distributions at small to moderate
$x$ values. We investigate the renormalisation/factorisation scale uncertainty
present in the normalisation and shape of the distribution at next-to-leading
order. We discuss specific slices of the distribution, the same-side/opposite
side ratio and the signed pseudorapidity distribution, in detail and compare
them with preliminary experimental data.
