@techreport{DoeZufallFall2010,
  author    = {Doe, John and Zufall, Rainer and Fall, Klara},
  title     = {This is a pdf test document},
  series = {This is a parent title},
  journal   = {This is a parent title},
  year      = {2010},
  abstract  = {This is a pdf test document},
  subject      = {Informationssystem},
  language  = {en}
}
@article{DoeZufall2009,
  author    = {Doe, John and Zufall, Rainer},
  title     = {This is a xhtml test document},
  year      = {2009},
  abstract  = {This is a xhtml test document},
  subject      = {Informationssystem},
  language  = {en}
}