The 13th immortal
By: by Robert Silverberg
Contributors: Gunn, James E., 1923-
Series: Ace double novel books -- D-223
Publisher: Ace Books
Published: 1957
Place of publication: New York
Language: eng
Number of pages: 190
Subjects: Science fiction
Notes: With (inverted): This fortress world/James E. Gunn. New York : Ace, [c1955].

R. Reginald.  Science fiction and fantasy literature : a checklist 1700-1974, p. 477.