Philip Handler to Richard P. Feynman, July 31, 1969 / Richard P. Feynman to Philip Handler, August 14, 1969 / Richard P. Feynman to Francis D. Murnaghan, January 22, 1970 / Richard P. Feynman to J. Neyman, April 28, 1970 by Philip Handler & Michelle Feynman narrated by Johanna Parker / Richard P. Feynman narrated by Richard Poe