Não informado. Outdoor Recreation Research. U.S. Department of the Interior, Bureau of Outdoor Recreation.
শিকাগো স্টাইল (17 তম সংস্করণ) উদ্ধৃতিNão informado. Outdoor Recreation Research. Washington: U.S. Department of the Interior, Bureau of Outdoor Recreation.
M.L.A (8 ম সংস্করণ) উদ্ধৃতিNão informado. Outdoor Recreation Research. U.S. Department of the Interior, Bureau of Outdoor Recreation.
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