@article{XiaGerhardKuenstleretal.1999,
  author    = {Xia, Zhongfu and Gerhard, Reimund and K{\"u}nstler, Wolfgang and Wedel, Armin and Danz, Rudi},
  title     = {High surface-charge stability of porous polytetrafluoroethylene electret films at room and elvated temperatures},
  year      = {1999},
  language  = {en}
}
@article{GerhardKuenstlerGoerneetal.2000,
  author    = {Gerhard, Reimund and K{\"u}nstler, Wolfgang and G{\"o}rne, Thomas and Pucher, Andreas and Weinhold, Till and Seiß, Martin and Xia, Zhongfu and Wedel, Armin and Danz, Rudi},
  title     = {Porous polytetrafluoroethylene space-charge electrets for piezoelectrical applications},
  year      = {2000},
  language  = {en}
}
@article{EllingPinnowDanzetal.2001,
  author    = {Elling, B. and Pinnow, M. and Danz, Rudi and Wegener, Michael and Wirges, werner and Gerhard, Reimund},
  title     = {Coating of porous polytetrafluoroethylene films with other polymers for electret applications},
  isbn      = {0-7803-7053-8},
  year      = {2001},
  language  = {en}
}