Publicado en: This is a transcript of the talk given by Dr. Feynman on December 29 and first published in Engineering and Science magazine, vol. XXIII, no. 5, February 1960, Pages 22-36.
Publicado en: Proceedings of the Fourth Berkeley Symposium on Mathematical Statistics and Probability (June 20-July 30 1960), Volume I: Contributions to the theory of statistics, pages 611-644.