Letter from [Ivan Ivanovich] Yastrebtzov, September 25, 1831 (St. Petersbourg [St. Petersburg]), Box: 24, Folder: 63. Letters, literary manuscripts, and personal papers of the Porter family, MS 28. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/467308 Accessed May 24, 2024.