John Stuart Mill (2017). “The Collected Works of John Stuart Mill: Utilitarianism, The Subjection of Women, On Liberty, Principles of Political Economy, A System of Logic, Ratiocinative and Inductive, Memoirs…”, p.3190, e-artnow
John Stuart Mill, Stephen Nathanson (1875). “Principles of Political Economy (Abridged): With Some of Their Applications to Social Philosophy”, p.291, Hackett Publishing
John Stuart Mill (2017). “John Stuart Mill: Life, Life Lessons & Achievements: Childhood and Early Education, Moral Influences in Early Youth, Youthful Propagandism, Completion of the "System of Logic", Publication of the "Principles of Political Economy", Parliamentary Life”, p.25, Madison & Adams
John Stuart Mill “Principles of Political Economy: Abridged with Critical, Bibliographical and Explanatory Notes and a Sketch of the History of Political Economy”, Library of Alexandria
John Stuart Mill (1858). “A System of Logic, Ratiocinative and Inductive: Being a Connected View of the Principles of Evidence and the Methods of Scientific Investigation”, p.426