Thomas Hobbes (1750). “The Moral and Political Works To which is Prefixed the Autors Life, Extracted from that Said to be Written by Himself ... Illustr. by the Ed. - London 1750”, p.148
Charles Darwin, James T. Costa (2009). “The Annotated Origin: A Facsimile of the First Edition of On the Origin of Species”, p.244, Harvard University Press