@misc{indiciaec3cdf041423d,
  title = {Ionospheric profile inversion using oblique-incidence ionograms},
  author = {Nielson, D. L. and Watt, T. M.},
  year = {1972},
  url = {https://ntrs.nasa.gov/citations/19730002880},
  note = {Source identifier: 19730002880}
}