Journey to the Center of the Earth published by Ace #M-119 with

1956 copyright and no other date.  

 20,000 Leagues Under the Sea published by Scholastic Magazine

in 1967, 5th edition.

Journey to the Center of the Earth:  Edgewear, shelf wear, creases and smudging on cover, wear on spine, yellowing of pages consistent with age.  Tight, square and unmarked.   20,000 Leagues:  edgewear, shelf wear, bumped corners, wear at spine, light creasing on front and back covers.  Tight square and unmarked.  See photos

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