Richard Whately (2010). “Elements of Rhetoric: Comprising an Analysis of the Laws of Moral Evidence and of Persuasion, with Rules for Argumentative Composition and Elocution”, p.1, SIU Press
Margaret Sanger, Michael W. Perry, H. G. Wells (2003). “The Pivot of Civilization in Historical Perspective: The Birth Control Classic”, p.40, Inkling Books
George Henry Lewes (1864). “Aristotle: a chapter from the history of science including analyses of Aristotle's scientific writings”, p.126, London : Smith, Elder and Company