@article{deBeaudrapOsborneEisert2010,
  author    = {Niel de Beaudrap and Tobias J. Osborne and Jens Eisert},
  title     = {Ground states of unfrustrated spin Hamiltonians satisfy an area law},
  doi       = {10.1088/1367-2630/12/9/095007},
  url       = {http://iopscience.iop.org/1367-2630},
  year      = {2010},
}