5Yahnke C J, de Fox I G, Colman F. Mammalian species richness in Paraguay:the effectiveness of national parks in preserving biodiversity [J]. Biological Conservation,1998,84(3):263-268.
6Al-Rehaili A M, Alabdulaaly A I. Chemical and economical evaluation of groundwater treatment plants in Riyadh[J]. Water Resource,1999,33(15):3291-3302.
7Choi W S, Lee K J, Lee B W. Determining the value of reductions in radiation risk using the contingent valuation method [J]. Annals of Nuclear Energy,2001,28(14):1431-1445.
8Loomis J, Kent P, Strange L. Measuring the economic value of restoring ecosystem services in an impaired river basin:results from a contingent valuation survey [J]. Ecological Economics,2000,33(1):103-117.
9Unger J. Comparisons of urban and rural bioclimatological conditions in the case of a Central-European city [J]. International Journal of Biometeorol,1999,43(1):139-144.
10Lee C K, Han S Y. Estimating the use and preservation values of national park's tourism resources using a contingent valuation method [J]. Tourism Management, 2002,23(5):531-540.
