Gen. Tech. Rep. PNW-GTR-098. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 32 p USDA Forest Service
In: Klenosky, David B.; Fisher, Cherie LeBlanc, eds. Proceedings of the 2008 Northeastern Recreation Research Symposium; 2008 March 30 - April 1; Bolton Landing, NY. Gen. Tech. Rep. NRS-P-42. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 67-70.,2009, 引用: 0
In: Watts, Clifton E., Jr.; Fisher, Cherie LeBlanc, eds. Proceedings of the 2009 Northeastern Recreation Research Symposium. Gen. Tech. Rep. NRS-P-66. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northern Research Station: 257-263.,2010, 引用: 1
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