Sir George Clerk [of Penicuick, 6th bart (1787-1867)], Penicuik House, Edinburgh, to Messrs Spottiswoode Robertson, May 14,1816, Box: 1, Folder: 14. Spottiswoode & Robertson collection, MS 186. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/248809 Accessed December 11, 2024.