History of the British Radio Valve to 1940 p. 148 & 184
Babani, International Radio Tube Encyclopaedia p. 138 & 139
Universal Vade-Mecum, Electron Valves and Semiconductor Devices
Taschenbuch zum Röhren-Codex 1948/49
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Fin Stewart
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Anónimo 15 Coleccionista
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