@article{nakano_iio_yamauchi_1993, 
  title={Improvement in front-to-back ratio of a bifilar backfire helix by a flared open end}, 
  volume={41}, 
  DOI={10.1109/8.267363}, 
  number={11}, 
  publisher={Institute of Electrical and Electronics Engineers (IEEE)}, 
  author={Nakano and Iio and Yamauchi}, 
  year={1993}
  }