@misc{indiciaec0e7fbaff8df,
  title = {Hyperbolic Equations for Vacuum Gravity Using Special Orthonormal Frames},
  author = {Estabrook, F. B.},
  year = {1997},
  url = {https://ntrs.nasa.gov/citations/20060035428},
  note = {Source identifier: 20060035428}
}