"Biographies of Distinguished Scientific Men". Book by François Arago, as translated by Baden Powell, Robert Grant, and William Fairbairn, p. 365, 1859.
Henry Beston, Elizabeth Jane Coatsworth (2001). “The Best of Beston: A Selection from the Natural World of Henry Beston from Cape Cod to the St. Lawrence”, p.28, David R. Godine Publisher
"If the Universe is Teeming with Aliens-- where is Everybody? Fifty Solutions to the Fermi Paradox and the Problem of Extraterrestrial Life". Book by Stephen Webb, p. 150, quoting "Inaugural Lecture as Professor of Astronomy, Gresham College", 2002.