History of the British Radio Valve to 1940 p. 144 & 198
Babani, International Radio Tube Encyclopaedia p. 20 & 21
Universal Vade-Mecum, Electron Valves and Semiconductor Devices
Taschenbuch zum Röhren-Codex 1948/49
15D2: Manufacturer's Literature
Emilio Ciardiello
Mas ...
15D2: Telefunken Werkstattbuch
Wolfgang Bauer
Mas ...
Just Qvigstad
15D2: Brimar Valve Manual 1947-8
Adrian Riesen
Mas ...