@misc{indiciae91be9af21644,
  title = {Method and apparatus for measuring frequency and phase difference},
  author = {Shores, Paul and Lichtenberg, Christopher and Kobayashi, Herbert S. and Cunningham, Allen R.},
  year = {1986},
  url = {https://ntrs.nasa.gov/citations/19870009259},
  note = {Source identifier: 19870009259}
}