^Getty, J Arch and Naumov, Oleg V. (2010). The Road to Terror, Stalin and the Self-Destruction of the Bolsheviks, 1932-1939. New Haven: Yale U.P. p. 49. ISBN978-0-300-10407-3.{{cite book}}: CS1 maint: multiple names: authors list (link)
^Getty, J. Arch. Origins of the Great Purges. pp. 121–122 and 245–246.