The Forbidden and Unmovable Years of the Tsar Fedor Ivanovich by R.G. Skrynnikov (in Russian), Box: 6, Folder: 4. Personal papers of John T. Alexander, PP 46. University of Kansas. Kenneth Spencer Research Library. https://archives.lib.ku.edu/repositories/3/archival_objects/221604 Accessed May 14, 2024.