@article{xiao_norgren_he_2011, 
  title={COMPACT THIRD-ORDER MICROSTRIP BANDPASS FILTER USING HYBRID RESONATORS}, 
  volume={19}, 
  DOI={10.2528/pierc10092706}, 
  publisher={EMW Publishing}, 
  author={Xiao and Norgren and He}, 
  year={2011}
  }