Tube Lore (II) p. 62
Babani, International Radio Tube Encyclopaedia p. 156 & 157
Taschenbuch zum Röhren-Codex 1948/49
Röhrencodex , Röhren-Taschenbuch 1950 23000 Röhren
VR67: Manufacturer's Literature
Emilio Ciardiello
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Just Qvigstad
VR67: Manufacturer's Literature
Emilio Ciardiello
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