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This Ace Science Fiction Book contains the complete text of the
original hardcover edition. It has been completely reset in a typeface
designed for easy reading, and was printed from new film.
PRINTING HISTORY
Twayne edition/ 1952
Ace edition/ June 1983
Copyright © 1952 by Twayne Publishers, Inc.
Copyright © renewed 1983 by Charter Communications, Inc.
Introduction © 1952, 1983 by Dr. John D. Clark
New Introduction © 1983 by John F. Carr
Cover art by Gino D'Achille
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