Jacques F. Vallee
professional works
Professional Works
fiction
Fiction
personal research
Personal Research

Challenge to Science
The UFO Enigma English-language editions

First U.S. edition

First U.S. edition
Chicago: Henry Regnery, 1966
Hardcover

 First British edition

First British edition
London: Neville Spearman, 1967
Hardcover

 First U.S. mass paperback

First U.S. mass paperback
New York: Ace, 1967

First Ballantine edition

First Ballantine edition
New York: December, 1974

 Fifth Ballantine edition

Fifth Ballantine edition
New York: May, 1989

 First British mass paperback

First British mass paperback
London: Tandem, 1974