Richard Whately (1872). “Elements of Rhetoric: Comprising an Analysis of the Laws of Moral Evidence and of Persuasion, with Rules for Argumentative Composition and Elocution”, p.29
Richard Whately (1858). “Elements of Rhetoric: Comprising an Analysis of the Laws of Moral Evidence and of Persuasion : with Rules for Argumentative Composition and Elocution”, p.247