America the beautiful [electronic resource] : promoting our national parks as travel destinations : hearing before the Subcommittee on Competitiveness, Innovation, and Export Promotion of the Committee on Commerce, Science, and Transportation, United States Senate, One Hundred Eleventh Congress, second session, April 27, 2010.
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Washington : U.S. G.P.O. : For sale by the Supt. of Docs., U.S. G.P.O., 2011.