Francillon, René J. McDonnell Douglas Aircraft since 1920: Volume II. Annapolis, Maryland: Naval Institute Press, 1990. ISBN1-55750-550-0.
McDonald, John J. Howard Hughes and the Spruce Goose. Blue Ridge Summit, Pennsylvania: Tab Books Inc., 1981. ISBN0-8306-2320-5.
Odekirk, Glenn E. Spruce Goose (Title inside cover: HK-1 Hercules: A Pictorial History of the Fantastic Hughes Flying Boat). Long Beach, California: Glenn E. Odekirk and Frank Alcantr, Inc., 1982. No ISBN.
Parker, Dana T. Building Victory: Aircraft Manufacturing in the Los Angeles Area in World War II, Cypress, CA, 2013. ISBN978-0-9897906-0-4.