APA (7th ed.) Citation

Heard, G. (1951). Is another world watching?: The riddle of the flying saucers ([1st ed.].). Harper.

Chicago Style (17th ed.) Citation

Heard, Gerald. Is Another World Watching?: The Riddle of the Flying Saucers. [1st ed.]. New York: Harper, 1951.

MLA (9th ed.) Citation

Heard, Gerald. Is Another World Watching?: The Riddle of the Flying Saucers. [1st ed.]. Harper, 1951.