Sir George Biddell Airy (1855). “Lecture on the Pendulum-experiments at Harton Pit: Delivered in the Central Hall, South Shields, October 24, 1854”, p.4
John Milton (1824). “The Poetical Works of John Milton: With Notes of Various Authors, Principally from the Editions of Thomas Newton, Charles Dunster and Thomas Warton ; to which is Prefixed Newton's Life of Milton”, p.40