Birdsall, S. S. (1992). Outline of American geography: Regional landscapes of the united States (4th ed.). John Willey.
Chicago-viite (17. p.)Birdsall, Stephen S. Outline of American Geography: Regional Landscapes of the United States. 4th ed. California: John Willey, 1992.
MLA-viite (9. p.)Birdsall, Stephen S. Outline of American Geography: Regional Landscapes of the United States. 4th ed. John Willey, 1992.
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