Ley, Willy (October 1968). "The Orbit of Explorer-1". For Your Information. Galaxy Science Fiction. pp. 93–102.
books.google.com
Everett, William. On the Cam: Lectures on the University of Cambridge in England. Cambridge, Mass.: Sever and Francis, 1865, p. 192.
dga.org
Weide, Robert (Summer 2012). "The Outer Limits". DGA Quarterly. Los Angeles, California: Directors Guild of America, Inc.: 64–71. A gallery of behind-the-scenes shots of movies featuring space travel or aliens. Page 68, photo caption: "Directed by Fritz Lang (third from right), the silent film "Woman in the Moon" (1929) is considered one of the first serious science fiction films and invented the countdown before the launch of a rocket. Many of the basics of space travel were presented to a mass audience for the first time."