Livingstone, David, 1813-1873. Letter to John Kirk 2 and Robert L. Playfair, 30 May 1869. Images copyright National Library of Scotland. Creative Commons Share-alike 2.5 UK: Scotland (https://creativecommons.org/licenses/by-nc-sa/2.5/scotland/). As relevant, copyright Dr. Neil Imray Livingstone Wilson. Creative Commons Attribution-NonCommercial 3.0 Unported (https://creativecommons.org/licenses/by-nc/3.0/). 