Wang, H., & Whittington, D. (2000). Willingness to pay for air quality improvements in Sofia, Bulgaria. World Bank.
Lua i Stíl Chicago (17ú heag.)Wang, Hua, agus Dale Whittington. Willingness to Pay for Air Quality Improvements in Sofia, Bulgaria. Washington, D.C: World Bank, 2000.
Lua MLA (9ú heag.)Wang, Hua, agus Dale Whittington. Willingness to Pay for Air Quality Improvements in Sofia, Bulgaria. World Bank, 2000.
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