Hughes HK-1 (H-4) Flying Boat Manual
U.S. War Department | English | paperback | 170 p. | 2009
Howard's Whirlybirds : Howard Hughes' Amazing Pioneering Helicopter Exploits
Donald J. Porter | English | hardback | 240 p. | 2013
AH-64 Apache
Christian Rastätter | German | hardback | 224 p. | 2021
AH-64 Apache Attack Helicopter
Headquarters Department of the Army | English | paperback | 656 p. | 2011
The Apache in European Service
Darren Willmin | English | paperback | 96 p. | 2016