@misc{indiciae8c15a9a5ab5a,
  title = {Preliminary Goddard geopotential using optical tracking data and a comparison with SAO models},
  author = {Lerch, F. J. and Wagner, C. A. and Putney, B. H. and Nickerson, K. G.},
  year = {1971},
  url = {https://ntrs.nasa.gov/citations/19720005238},
  note = {Source identifier: 19720005238}
}