1. Ionospheric Sounding Using Real-Time Amateur Radio Reporting Networks
2. Levis, C.A., Johnson, J.T. and Teixeira, F.L. (2010) Radiowave Propagation: Physics and Applications. http://ci.nii.ac.jp/ncid/BB03015333
3. Hepburn, W. (2023) LW Radio Beacons. https://www.dxinfocentre.com/ndb.htm
4. NIST (2023) Radio Station WWV.
https://www.nist.gov/pml/time-and-frequency-division/time-distribution/radio-station-wwv
5. Federal Communications Commission. AM Station Classes, and Clear, Regional, and Local Channels.
https://www.fcc.gov/media/radio/am-clear-regional-local-channels