Não informado. Outdoor Recreation Research. U.S. Department of the Interior, Bureau of Outdoor Recreation.
Citação do estilo Chicago (17ª ed.)Não informado. Outdoor Recreation Research. Washington: U.S. Department of the Interior, Bureau of Outdoor Recreation.
Citação MLA (8ª ed.)Não informado. Outdoor Recreation Research. U.S. Department of the Interior, Bureau of Outdoor Recreation.
Предупреждение: эти цитированмия не могут быть всегда правильны на 100%.