1. City of Bradford Technical College, Calendar for the 32nd Session,1913-1914, City of Bradford Education Committee, 1913 (Personal Collection of P.S. Excell, Bradford University).
2. The view that Appleton felt himself to have been lucky to have acquired a valve (or valves) by a chance capture from the opposing side is well established. This, however, is surprising, since triodes were in serial production in the UK from 1916. It must be presumed that they were deemed to be inap-propriate for British Army use, but this matter merits further investigation.
3. IX. Note on the effects of grid currents in three-electrode ionic tubes
4. MS 2300/E117, letter from Appleton to Van der Pol, 4 May 1920.
5. XXV. On the form of free triode vibrations