@misc{indiciae8de33027a04e,
  title = {Tracking Gravity Probe B gyroscope polhode motion},
  author = {Keiser, George M. and Parkinson, Bradford W. and Cohen, Clark E.},
  year = {1990},
  url = {https://ntrs.nasa.gov/citations/19900060618},
  note = {Source identifier: 19900060618}
}