@article{bhattacharyya:1988:ra,
    author = {Bhattacharyya, A. and Shafai, L.},
     title = {Theoretical and experimental investigation
              of the elliptical annual ring antenna},
   journal = {IEEE Trans. Antennas and Propagation},
    volume = {36},
      year = {1988},
    number = {11},
     pages = {1526–1530},
       doi = {10.1109/8.9700}}