Livingstone, David, 1813-1873. Letter to William K. Tweedie, 2, 18 November 1861, 1 March 1862. 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/). 