* The losses are basically as given in the official history, The Defence of the United Kingdom (HMSO, London, 1957). They were compiled from Fighter Command sources on the British side, Luftwaffe Quartermaster-General sources on the German. Since then further work has been done, notably by Francis K. Mason in his Battle over Britain (McWhirter Twins, London, 1969) and by researchers for the After the Battle publications, to refine and correct these figures, in particular by distinguishing losses in combat from those arising from other causes. However, no other set of figures has yet been given official status, and these from the official history, if not unchallengeable in detail, give a sufficiently clear indication of the scale of activity and the ratio of success.