The National Archives, Kew, London

HW 5/4 and HW 5/5: Government Code and Cypher School, German Section: Reports of German Army and Air Force High Grade Machine Decrypts (CX/FJ and CX/JQ Reports) (4 August–10 October 1940)

HW 13/28: German Naval Air Activity Vol. II: Carrier- and land-based units (28 Dec 1939–31 Dec 1940)

HW 48/1: Intelligence reports and correspondence concerning German preparations for the invasion of Britain (17 May 1940–4 March 1941)

Online:

Celluloid incendiary bombs: https://apps.dtic.mil/sti/pdfs/ADA474302.pdf

Phases of the Battle of Britain: https://www.rafmuseum.org.uk/research/online-exhibitions/history-of-the-battle-of-britain/introduction-to-the-phases-of-the-battle-of-britain/