Note XIII-1a — Chapter XIII · INVESTIGATORS: AIR FORCE AND CIVILIAN
Reading edition
Tacker, L. J. Flying Saucers and the U. S. Air Force. Princeton, N.J.: D. Van Nostrand Co., 1960.
[XIII-2] Keyhoe, D. E. Flying Saucers from Outer Space. New York: Henry Holt & Co., 1953.