Billington, R. A. (1979). Westward to the Pacific: An overview of America's westward expansion. Jefferson National Expansion Historical Association.
Style de citation Chicago (17e éd.)Billington, Ray Allen. Westward to the Pacific: An Overview of America's Westward Expansion. St. Louis (Mo.): Jefferson National Expansion Historical Association, 1979.
Style de citation MLA (8e éd.)Billington, Ray Allen. Westward to the Pacific: An Overview of America's Westward Expansion. Jefferson National Expansion Historical Association, 1979.
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