Gnome Press, 1950; Ace, 1953 & 1981; Lancer, 1967; Sphere, 1974; Prestige, 1977. Reprinted numerous times by several publishers between 1950 and 1994. Gnome Press cover by John Forte. 1953 Ace edition cover by Norman Saunders.All other editions have a cover by Frank Frazetta with varying graphics and borders. The 1953 Ace edition was published as a double novel with The Sword of Rhiannon by Leigh Brackett. Out of print.