@misc{indiciaeac305785e269,
  title = {Changes of lower ionosphere electron concentrations with solar activity.},
  author = {Mechtly, E. A. and Bowhill, S. A. and Smith, L. G.},
  year = {1972},
  url = {https://ntrs.nasa.gov/citations/19730027227},
  note = {Source identifier: 19730027227}
}