The High Frequency Benchmark Propagation Program, J.A. Ferguson, C.H. Shellman, October 1993
NRaD TD 2609 (PDF format)
Atmospheric Effects Assessment Program: Ionospheric Sounding, R.A. Sprague, February 1994
NRaD TD 2730 (PDF format)
Measurements of Ionospheric Variability, October 1994