William Jennings Bryan, Joe Cain (2009). “William Jennings Bryan's Last Message: A Reprint of His Famous Closing Arguments for the 1925 Scopes Monkey Trial, Undelivered and Posthumously Published”, p.14, Lulu.com
Charles Lyell (1873). “The Geological Evidence of the Antiquity of Man with an Outline of Glacial and Post-tertiary Geology and Remarks on the Origin of Species with Special Reference to Mans First Appearance on the Earth by Charles Lyell”, p.202