  An interesting type of spin chain has appeared in the context of the planar
AdS/CFT correspondence: It is based on an integrable nearest-neighbor spin
chain, and it is perturbatively deformed by long-range interactions which
apparently preserve the integrable structure. Similar models can be constructed
by demanding the existence of merely one conserved local charge. Although the
latter is not a sufficient integrability condition in general, the models often
display convincing signs of full integrability.
  Here we consider a class of long-range spin chains with spins transforming in
the fundamental representation of gl(N). For the most general such model with
one conserved local charge we construct a conserved Yangian generator and show
that it obeys the Serre relations. We thus provide a formal proof of
integrability for this class of models.
