 The Garaburda scene (exceptionally important for the play's structure, according to the author's "Production plan") has been totally made up, but again, some details involved have been taken from Karamzin (Mikhail Garaburda's negotiations with Grozny in 1573, among others).Apart from Karamzin's "History" Tolstoy used, albeit to a lesser extent, "Tales of Prince Kurbsky", published in 1831 by N.Ustryalov.Kurbsky's letters in Scene 2, Act 1, present a mosaic of his real letters, the 1679 one featuring most prominently.