@misc{indiciaee3d2d9e0fa0c,
  title = {An improved model for the Earth's gravity field},
  author = {Tapley, B. D. and Shum, C. K. and Yuan, D. N. and Ries, J. C. and Schutz, B. E.},
  year = {1989},
  url = {https://ntrs.nasa.gov/citations/19900011199},
  note = {Source identifier: 19900011199}
}