Mark Hopkins (1852). “Receiving and Giving: A Baccalaureate Sermon, Delivered at Williamstown , Ms. August 15, 1852. Published by Request of the Class”, p.20
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.548