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
HL13: Telefunken Werkstattbuch
Wolfgang Bauer
Just Qvigstad
HL13: My schematic collection.
Pier Antonio Aluffi