@conference{7651,
  author = {D. Larden and Peter Bender},
  title = {Preliminary Study of GPS Orbit Determination Accuracy Achievable from Worldwide Tracking Data},
  year = {1983},
  publisher = {Las Cruces, NM, New Mexico State University},
  address = {Las Cruces, NM},
  note = {JILA Pub. 2452},
}