  For the past two decades the Villain-Lai-Das Sarma equation has served as the
theoretical framework for conserved surface growth processes, such as
molecular-beam epitaxy. However some phenomena, such as mounding, are yet to be
fully understood. In the following, we present a systematic analysis of the
full, original Villain-Lai-Das Sarma equation showing that mound forming terms,
which should have been included initially on symmetry grounds, are generated
under renormalisation. A number of widely studied Langevin equations are
recovered as limits or trivial fixed points of the full theory.
