PUBLICATION HISTORY Analog, December 1960. Analog, April 1961. (British edition), p.35-53. Illustrated by Leo Summers. Rulers of Men, edited by Hans Stefan Santesson. New York: Pyramid Books, 1965, pbk, p.135-159. as: "Der K-Faktor" in: Die Mächtigen des Universums, edited by Hans Stefan Santesson. Munich: Heyne, 1970. Translated by Birgit Ress-Bohusch. [German] 50 in 50, July 2001.