  This paper analyses the parabolic geometries generated by a free
3-distribution in the tangent space of a manifold. It shows the existence of
normal Fefferman constructions over CR and Lagrangian contact structures
corresponding to holonomy reductions to SO(4,2) and SO(3,3), respectively.
There is also a fascinating construction of a `dual' distribution when the
holonomy reduces to $G_2'$. The paper concludes with some holonomy
constructions for free $n$-distributions for $n>3$.
