@article{GrossNesmeVogtsetal.2012,
  author    = {David Gross and V. Nesme and H. Vogts and Reinhard F. Werner},
  title     = {Index theory of one dimensional quantum walks and cellular automata},
  journal   = {Communications in mathematical physics},
  volume    = {310},
  number    = {2},
  pages     = {419 -- 454},
  doi       = {10.1007/s00220-012-1423-1},
  year      = {2012},
}