@article{
  author = {K.-D. Kammeyer and H. Schenk},
  year = {1980},
  month = {Jan},
  title = {Messtechnische Untersuchungen zur Datenuebertragung \"{u}ber Fernsprechkanaele},
  volume = {34},
  number = {4},
  pages = {109-117},
  journal={Frequenz}
}