- "Simplex" The IEEE Authoritative Dictionary of Standard Terms, 7th Ed., 2000, Inst. of Electrical and Electronic Engineers, p.1053
- Milnor, J.W. and G.A. Randall. "The Newfoundland-Azores High-Speed Duplex Cable". A.I.E.E. Electrical Engineering. May 1931
- Report of the Committee on Public Emergency Service Communication. NFPA 1221, May, 2002.
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