@article{CramerEisert2006,
  author    = {Marcus Cramer and Jens Eisert},
  title     = {Correlations, spectral gap and entanglement in harmonic quantum systems on generic lattices},
  doi       = {10.1088/1367-2630/8/5/071},
  url       = {http://iopscience.iop.org/1367-2630},
  year      = {2006},
}