Babani, International Radio Tube Encyclopaedia p. 92 & 93
- - Manufacturers Literature
Universal Vade-Mecum, Electron Valves and Semiconductor Devices
Taschenbuch zum Röhren-Codex 1948/49
D404: ficha de valvulas
Getulio Jimenez-Gomez
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D404: g.h.
Gerhard Heigl
Just Qvigstad
D404: Philips Verstärkerröhren
Gerhard Heigl
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