Third Rome
The only biography in English of Ivan is J. L. I. Fennell's "Ivan the Great of Moscow" (1961). The Third Rome concept is discussed in Nicholas Zernov's "Moscow: The Third Rome" (1937). A firsthand account of the 1486–1506 period is Baron Sigismund von Herberstein's "Notes upon Russia", translated and edited by R. H. Major (2 vols., 1851–1852). The most thorough study of this period available to the English reader is George Vernadsky and Michael Karpovich's "A History of Russia, vol. 4" (1959).