Albert Einstein (2015). “Bite-Size Einstein: Quotations on Just About Everything from the Greatest Mind of the Twentieth Century”, p.32, St. Martin's Press
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
Dorothea Waley Singer, Giordano Bruno (1968). “Giordano Bruno; his life and thought: With annotated translation of his work, On the infinite universe and worlds”, Greenwood Pub Group
"The Impact of Space Activities Upon Society". Book co-sponsored by The International Academy of Astronautics and The European Space Agency, February 2005.