Sir William BLACKSTONE, Samuel Warren (1856). “Blackstone's Commentaries systematically abridged and adapted to the existing state of the law and constitution, with great additions. By Samuel Warren”, p.101
Molotov's report on (29 March 1940), after the Polish defeat, as quoted in the weekly Soviet newspaper "Moscow News", published by Mezhdunarodnaya Kniga, April 1, 1940.