National Council for Geographic Education (1994). "National Geography Standards". Geography Education Standards Project. National Geographic Society Committee on Research and Exploration. Archived from the original on 2008-02-09. Retrieved 2008-06-24.
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National Council for Geographic Education (1994). "National Geography Standards". Geography Education Standards Project. National Geographic Society Committee on Research and Exploration. Archived from the original on 2008-02-09. Retrieved 2008-06-24.