@misc{indiciae12ad40a20355,
  title = {Tests Of A Differential Global Positioning System},
  author = {Edwards, F. G. and Hegary, D. M. and Turner, R. N. and Van Graas, F. and Sharma, S.},
  year = {1990},
  url = {https://ntrs.nasa.gov/citations/19900000521},
  note = {Source identifier: 19900000521}
}