"Photons: Corpuscles of Light". Richard P. Feynman's lecture 1 at the Sir Douglas Robb lectures at the University of Auckland, New Zealand, www.youtube.com. 1979.
Richard P. Feynman's letter to Koichi Mano (February 3, 1966), as quoted in "Perfectly Reasonable Deviations from the Beaten Track: The Letters of Richard P. Feynman" edited by Michelle Feynman and Timothy Ferris (pp. 198, 201), April 5, 2005; also quoted in "Wise Man" by Freeman Dyson, www.nybooks.com. October 20, 2005.