"List of Engagements for the Emperor of Russia, King of Prussia, with his two sons and two brothers when they came to London", 7-21 June 1814, Box: 6, Folder: 4G:21. Sotheby Family Papers, MS 4. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/262046 Accessed May 21, 2024.