@article{KleinRosenberger2009,
  author    = {Markus Klein and Elke Rosenberger},
  title     = {Harmonic approximation of difference operators},
  doi       = {10.1016/j.jfa.2009.09.004},
  url       = {http://www.sciencedirect.com/science/journal/00221236},
  year      = {2009},
}