Sir Charles Lyell (1845). “Travels in North America, in the Years 1841-2: With Geological Observations on the United States, Canada, and Nova Scotia”, p.15
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