Book Jan Forsgren (2021)
The Fieseler Fi 156 Storch: The First STOL Aircraft. (/isis/citation/CBB074096626/) unapi

Book Peter de Jong (2021)
Arado Ar 196 Units in Combat. (/isis/citation/CBB005310601/) unapi

Article Donald M. Bishop; Erik R. Limpaecher (2021)
Looking Back from the Age of ISR: U.S. Observation Balloons in WWI. Air Power History (pp. 7-18). (/isis/citation/CBB684109801/) unapi

Book Tyler Morton (2019)
From Kites to Cold War: The Evolution of Manned Airborne Reconnaissance. (/isis/citation/CBB997279151/) unapi

Book Rick Bishop (2017)
Shady Lady: Flying the U-2 Spy Plane. (/isis/citation/CBB686233970/) unapi

Book Norman Polmar; John Bessette (2016)
Spyplanes: The Illustrated Guide to Manned Reconnaissance and Surveillance Aircraft from World War I to Today. (/isis/citation/CBB025553319/) unapi

Book Richard H. Graham (2016)
SR–71 Flight Manual, The Official Pilot’s Handbook, Declassified and Expanded with Commentary. (/isis/citation/CBB689207747/) unapi