»Concerning Mark Twain«. The Week : a Canadian journal of politics, literature, science and arts. 1 (11): 171. 14. februar 1884. Pridobljeno 26. aprila 2013.
Philip S. Foner, Mark Twain: Social Critic (New York: International Publishers, 1958), p. 13, cited in Helen Scott's "The Mark Twain they didn't teach us about in school" (2000) in the International Socialist Review 10, Winter 2000, pp. 61–65, at [1]