History of the British Radio Valve to 1940 p. 152
Babani, International Radio Tube Encyclopaedia p. 110 & 111
Universal Vade-Mecum, Electron Valves and Semiconductor Devices
Taschenbuch zum Röhren-Codex 1948/49
HP4115: Telefunken Werkstattbuch
Wolfgang Bauer
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