Advisory Group for Research and Development (AGARD) (2 October 1992). ELF/VLF/LF Radio Propagation and Systems Aspects(PDF) (Report). North Atlantic Treaty Organization (NATO). Retrieved 16 December 2024.
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US 4580111, Swanson, Hilmer, "Amplitude modulation using digitally selected carrier amplifiers", published 1 April 1986, assigned to Harris Corp