Graf, B. (2001). Gems: The world's greatest treasures and their stories. Prestel.
Chicago-viite (17. p.)Graf, Bernhard. Gems: The World's Greatest Treasures and Their Stories. Munich: Prestel, 2001.
MLA-viite (9. p.)Graf, Bernhard. Gems: The World's Greatest Treasures and Their Stories. Prestel, 2001.
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