@misc{indiciae13b0124ec1b2,
  title = {Two-axis controller Patent},
  author = {Ballard, R. R. and Musick, R. O. and Robertson, W. L.},
  year = {1967},
  url = {https://ntrs.nasa.gov/citations/19700032757},
  note = {Source identifier: 19700032757}
}