Watkins, J. E. (1919). Famous mysteries: Curious and fantastic riddles of human life that have never been solved. John C. Winston Co..
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Watkins, John Elfreth. Famous Mysteries: Curious and Fantastic Riddles of Human Life That Have Never Been Solved. Philadelphia: John C. Winston Co., 1919.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Watkins, John Elfreth. Famous Mysteries: Curious and Fantastic Riddles of Human Life That Have Never Been Solved. John C. Winston Co., 1919.
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