UK National Archives: RAF Wing and Squadron Operations Record Books and pilots’ sortie reports; daily intelligence/operations summaries of the Mediterranean Allied Tactical Air Force and Mediterranean Allied Coastal Air Force; Ultra decrypts for February, March and April 1944; MAAF Signals Intelligence material; prisoner of war interrogation reports.

Loss data for I./JG 2 via Ferdinando D’Amico.

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

Information on USAAF claims and losses; on the loss of an Auster of No. 655 Squadron; and the crash-landing of 4./JG 2's Oblt. Schneider kindly contributed by Christopher Shores from his own extensive researches into the Mediterranean Air War.

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

Online USAAF MACRs at http://www.footnote.com

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

321st Bombardment Group operational diary: http://www.warwingsart.com/12thAirForce/321history.html

Extract from the Flugbuch of Ofw. Fritz Hartmann from Phil Irwin.

Extract from the Flugbuch of Uffz. Walter Sauder from Erik Mombeeck.

Extracts from the 347th Fighter Squadron USAAF, Outline History, April 1944 via Ferdinando D’Amico.

Ernest R. McDowell and William N. Hess: Checkertail Clan: The 325th Fighter Group in North Africa and Italy by (Aero Publishers, 1969).

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).

Carlo D’Este, Fatal Decision: Anzio and the Battle for Rome (Fontana, 1992).

Tom Ivie and Paul Ludwig: Spitfires And Yellow Tail Mustangs: The 52nd Fighter Group in World War Two (Hikoki Publications Ltd., Crowborough, 2005) ISBN 1 902109 43 0.

Andrew Thomas: American Spitfire Aces of World War 2 (Osprey Publishing Ltd., 2007) ISBN 13: 978 1 84603 202 8.