四極真空管
Engineering Data Service 12K5. Emporium, PA: Sylvania Electric Products Inc. Radio Tube Division, Emporium, PA. pp. 7. http://www.jogis-roehrenbude.de/Roehren-Geschichtliches/Niedrigspannungs-Roehren/12K5.pdf
↑ General Electric. FP-54 Description and Rating. ETI-160. Schenectady, NY: General Electric. pp. 1–5. http://frank.pocnet.net/sheets/141/f/FP54.pdf
↑ Dolezalek, H. (February 1963). Electrometer Tubes: Part II.. Washington: NATIONAL AERONAUTICS AND SPACE ADMINISTRATION. pp. 7. https://archive.org/stream/nasa_techdoc_19710066217/19710066217_djvu.txt
↑ Scott-Taggart, J. (1922). Elementary Text-Book on Wireless Vacuum Tubes, 4th Edition. Radio Press Ltd. pp. 207–8. https://archive.