Notes: • "Berkley Edition, December, 1955" • Printing not stated, no number line • "This book is based upon previously published stories By A. E. van Vogt: "Concealment" and "The Storm," copyright © 1943, by Street and Smith Publications, Inc., and "The Mixed Men," copyright © 1945, by Street and Smith Publications, Inc." stated on the copyright page. • Clute/Nicholls states this edition is 'cut' from the '52 first edition • US Edition, Canadian one has different price • The cover is credited to Powers on the copyright page • This first printing is different from the second printing in the ads in the back [first has an ad for Groff Conklin's Possible Worlds of SF issued by Berkley in July 1955] and that the second printing does not have the letters ANC above the price on the cover, otherwise the two are identical.