@article{deBeaudrapOhligerOsborneetal.2010,
  author    = {Niel de Beaudrap and Matthias Ohliger and Tobias J. Osborne and Jens Eisert},
  title     = {Solving frustration-free spin systems},
  doi       = {10.1103/Physrevlett.105.060504},
  url       = {http://prl.aps.org/},
  year      = {2010},
}