Richard Rhodes (2002). Masters of Death: The SS-Einsatzgruppen and the Invention of the Holocaust. New York: Alfred A. Knopf. ISBN0-375-40900-9. The invasion surprised the NKVD, whose jails and prisons in the annexed territories, despite earlier deportations, were crowded with political prisoners. Rather than releasing their prisoners as they hurriedly retreated during the first week of the war, the Soviet secret police killed most of them. In the first week of the invasion, the NKVD prisoner executions totaled some 10,000 in western Ukraine and more than 9,000 in Vinnytsia, eastward toward Kiev. Comparable numbers of prisoners were executed in eastern Poland, Byelorussia, Lithuania, Latvia, and Estonia. The Soviet areas had already sustained hundreds of thousands of executions during the 1937–1938 Great Purge.
Julian Siedlecki (1990). Losy Polaków w ZSRR w latach 1939-1986 (v poljščini). Edward Raczyński (3 izd.). London: Gryf Publications. str. 59. as cited in: Tadeusz Krahel. »Zginęli w końcu czerwca 1941 roku«. Czas Miłosierdzia. Arhivirano iz prvotnega spletišča dne 1. junija 2019. Pridobljeno 2. junija 2006.
Julian Siedlecki (1990). Losy Polaków w ZSRR w latach 1939-1986 (v poljščini). Edward Raczyński (3 izd.). London: Gryf Publications. str. 59. as cited in: Tadeusz Krahel. »Zginęli w końcu czerwca 1941 roku«. Czas Miłosierdzia. Arhivirano iz prvotnega spletišča dne 1. junija 2019. Pridobljeno 2. junija 2006.
