@article{Zimmermann2011,
  author    = {Zimmermann, Andreas},
  title     = {Einf{\"u}hrung : Folterpr{\"a}vention im v{\"o}lkerrechtlichen Mehrebenensystem},
  isbn      = {978-3-86956-104-2},
  year      = {2011},
  language  = {de}
}
@article{Zimmermann2011,
  author    = {Zimmermann, Andreas},
  title     = {Article 1 A, para. 2},
  isbn      = {978-0-19-954251-2},
  year      = {2011},
  language  = {de}
}