@misc{indiciaea73a3a0c910a,
  title = {On optimal filtering of GPS dual frequency observations without using orbit information},
  author = {Eueler, Hans-Juergen and Goad, Clyde C.},
  year = {1991},
  url = {https://ntrs.nasa.gov/citations/19910058694},
  note = {Source identifier: 19910058694}
}