Erasmus Darwin (1807). “The Botanic Garden: A Poem, in Two Parts: Part I. Containing The Economy of Vegetation. Part II. The Loves of the Plants”, p.22
"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.