@article{Stulpe2009,
  author    = {Stulpe, Werner},
  title     = {Density Operator},
  series = {Compendium of Quantum Physics : concepts, experiments, history and philosophy / Daniel Greenberger ... ed.},
  journal   = {Compendium of Quantum Physics : concepts, experiments, history and philosophy / Daniel Greenberger ... ed.},
  publisher = {Springer},
  address   = {Berlin},
  isbn      = {978-3-540-70622-9},
  pages     = {166 -- 169},
  year      = {2009},
  language  = {en}
}