Historians have suggested that Robert Smith Todd and Elizabeth Parker were double first cousins: his paternal aunt was married to her father, and her paternal aunt was married to his father.Mary Todd BiographyАрхивирано на сајту Wayback Machine (9. мај 2012)
Mary Todd Lincoln House, National Park Service, (June 9, 1977). Retrieved on September 14, 2011.
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Historians have suggested that Robert Smith Todd and Elizabeth Parker were double first cousins: his paternal aunt was married to her father, and her paternal aunt was married to his father.Mary Todd BiographyАрхивирано на сајту Wayback Machine (9. мај 2012)