@misc{indiciaedd6dcd97cc2e,
  title = {Gravity model improvement investigation},
  author = {Siry, J. W. and Kahn, W. D. and Bryan, J. W. and Vonbun, F. F.},
  year = {1973},
  url = {https://ntrs.nasa.gov/citations/19740006950},
  note = {Source identifier: 19740006950}
}