@article{WegenerBergweilerWirgesetal.2005,
  author    = {Michael Wegener and Steffen Bergweiler and Werner Wirges and Andreas Pucher and Enis Tuncer and Reimund Gerhard},
  title     = {Piezoelectric two-layer stacks of cellular polypropylene ferroelectrets : transducer response at audio and ultrasound frequencies},
  year      = {2005},
}