An account such as this has its limitations: it's only as good as its sources and a new one might change the picture considerably. Where several actions took place in the same general area during a day, information about the timing of individual events is especially important but is sometimes lacking or contradictory. I've tried to cover every engagement I found where Fw 190s were reported although in combat aircraft recognition was often unreliable — experience suggests that machines in different paint schemes could easily be "recognised" as different types. Victory claims on both sides are notoriously optimistic and often for the wrong type of aircraft.

UK National Archives: RAF Wing Operations Record Books; daily intelligence/operations summaries of the Mediterranean Allied Tactical Air Force and Mediterranean Allied Strategic Air Force; Ultra decrypts for May, June and July 1944; Signals Intelligence data; prisoner of war interrogation reports; Field Intelligence Party reports.

Bundesarchiv-Militärarchiv, Freiburg-im-Breisgau: orders of battle; SG 4 aircraft deliveries and losses for June 1944; Kriegstagebücher of Flughafenbereiche 2/VI and 18/XI; monthly aircraft deliveries to theatres of operations.

Loss data for I. and II./SG 4 via J. Richard Smith and Winfried Bock.

Other Luftwaffe claim and loss data from J. Richard Smith and Eddie J. Creek; Winfried Bock and Arno Abendroth via Ferdinando D’Amico.

Listings of USAAF Missing Air Crew Reports: http://www.armyairforces.com/dbmacr.asp

USAAF Missing Air Crew Reports at Fold3.com.

Website of the 324th Fighter Group: http://www.324thfighter.org/

Website of the 350th Fighter Group: http://web.me.com/vizcarraguitars/350th_Fighter_Group_Blog/350th_FG_Blog/350th_FG_Blog.html

Tony Wood’s listings of Luftwaffe claims: http://lesbutler.co.uk/claims/tonywood.htm

Deliveries of aircraft to and losses from SG 4 for January–May 1944 reproduced at: www.ww2.dk (originals at BA-MA, Freiburg); monthly aircraft deliveries to units in Italy;

Jochen Prien: Chronik des Jagdgeschwaders 53 Teil 3 (Stuve Druck, Eutin, 1991) and Chronik des Jagdgeschwaders 77 Teil IV (Stuve Druck, Eutin, 1995).

Christopher Shores: USAAF Fighter Units MTO 1942–45 (Osprey Publishing Ltd., 1978).

Various maps of Italy.