Não informado. Outdoor Recreation Research. U.S. Department of the Interior, Bureau of Outdoor Recreation.
توثيق أسلوب شيكاغو (الطبعة السابعة عشر)Não informado. Outdoor Recreation Research. Washington: U.S. Department of the Interior, Bureau of Outdoor Recreation.
توثيق جمعية اللغة المعاصرة MLA (الطبعة الثامنة)Não informado. Outdoor Recreation Research. U.S. Department of the Interior, Bureau of Outdoor Recreation.
تحذير: قد لا تكون هذه الاستشهادات دائما دقيقة بنسبة 100%.