David Hume (1788). “Essays, moral, political, and literary.- v. 2. An inquiry concerning human understanding. A dissertation on the passions. An inquiry concerning the principles of morals. The natural history of religion”, p.72
David Hume (1826). “The Philosophical Works: Including All the Essays, and Exhibiting the More Important Alterations and Corrections in the Successive Ed. Publ. by the Author”, p.9
David Hume, Thom Chittom (2004). “An Enquiry Concerning Human Understanding: And Selections from a Treatise of Human Nature”, p.200, Barnes & Noble Publishing