US National Archives National Archives and Records Administration, documents related to Committee to Investigate and Study the Facts, Evidence, and Circumstances of the Katyn Forest Massacre (1951–52) online, last accessed on 14 April 2010.
Truy cập 29 tháng 6 năm 2011.  ^ a ă National Archives and Records Administration, documents related to Committee to Investigate and Study the Facts, Evidence, and Circumstances of the Katyn Forest Massacre (1951–52) online, last accessed on ngày 14 tháng 4 năm 2010.