5Davis R K. Recreation Planning as an Economic Problem [ J ]. Natural Re- sources Journal[ J]. 1963, (3) :239 - 249.
6Loomis J B, Walsh R G. Recreation Economic Decisions:Comparing Benefits and Costs(2nd) ~ MJ. Venture Publishing Inc, 1997.
7Carson R T. Valuation of Tropical Rainforests : Philosophical and Practical Issues in the Use of Contingent Valuation[ J]. Ecological Economies, 1998, (24) : 15 - 29.
