William Butler Yeats, Richard J. Finneran, George Bornstein (2007). “The Collected Works of W.B. Yeats Volume IV: Early Essays”, p.51, Simon and Schuster
William Whewell (1847). “History of the Inductive Sciences: I. The Greek school philosophy, with reference to physical science. II. The physical sciences in ancient Greece. III. Greek astronomy. IV. Physical science in the middle ages. V. Formal astronomy after the stationary period”, p.10