Não informado. Outdoor Recreation Research. U.S. Department of the Interior, Bureau of Outdoor Recreation.
शिकागो शैली (17वां संस्करण) प्रशस्ति पत्रNão informado. Outdoor Recreation Research. Washington: U.S. Department of the Interior, Bureau of Outdoor Recreation.
एमएलए (8वां संस्करण) प्रशस्ति पत्रNão informado. Outdoor Recreation Research. U.S. Department of the Interior, Bureau of Outdoor Recreation.
चेतावनी: ये उद्धरण हमेशा 100% सटीक नहीं हो सकते हैं.