Heffner, R. D. (1956). A documentary History of the united states. The New American Library.
Lua i Stíl Chicago (17ú heag.)Heffner, Richard D. A Documentary History of the United States. New York: The New American Library, 1956.
Lua MLA (9ú heag.)Heffner, Richard D. A Documentary History of the United States. The New American Library, 1956.
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