Page 8: Recordings of Richard Feynman telling stories to Ralph Leighton, including Safecracker Suite, can be listened to for free here. (You can also download them for a modest fee.)

Page 26: Alan Leighton's English translation of Reise ins Asiatische Tuwa, with the title Journey to Tuva: an eyewitness account of Tuva in 1929, is out of print. 

A PDF can be obtained (with an honor-system commitment not to post it or pass it on) by emailing tuvamuch @ gmail.com (with no spaces) and requesting a copy.

Page 56: Archived newsletters from Friends of Tuva can be found here.

Page 233: A direct link to Ralph Leighton's 1991 article "Yurts, Yaks, and Fax Machines" can be found here.

Page 251: The album Tuva Talk, featuring Tuvan throat-singer Ondar along with Richard Feynman, Ralph Leighton, and Tom Rutishauser ("The Three Quarks") can be heard here. 

Page 251: Other Feynman and Ondar recordings can be found here.