Issue partially indexed - probably identical to the British issue of the same date except for the price marked on the cover.  | 
   
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 Issue partially indexed - probably identical to the British issue of the same date except for the price marked on the cover.  | 
   
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 Issue partially indexed - probably identical to the British issue of the same date except for the price marked on the cover.  | 
   
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 Issue partially indexed - probably identical to the British issue of the same date except for the price marked on the cover.  | 
   
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 Issue partially indexed - probably identical to the British issue of the same date except for the price marked on the cover.  | 
   
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 Issue partially indexed - probably identical to the British issue of the same date except for the price marked on the cover.  | 
   
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 Issue partially indexed - probably identical to the British issue of the same date except for the price marked on the cover.  | 
   
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 Issue partially indexed - probably identical to the British issue of the same date except for the price marked on the cover.  | 
   
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 Identical to the British issue of the same date except for the price marked on the cover. Details taken from Table of Contents.  | 
   
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 Issue partially indexed - probably identical to the British issue of the same date except for the price marked on the cover.  | 
   
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 Issue partially indexed - probably identical to the British issue of the same date except for the price marked on the cover.  | 
   
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 Issue partially indexed - probably identical to the British issue of the same date except for the price marked on the cover.  | 
   
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 Issue partially indexed - probably identical to the British issue of the same date except for the price marked on the cover.  | 
   
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 Strictly speaking the first 18 issues were titled Street & Smith’s Unknown (UK) but as the magazine is universally known as Unknown (UK) it has been decided to index it as such.  | 
  
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 Details supplied by Douglas Greene.  | 
   
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 Title changed from Unknown (UK).  | 
  
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