Altaf, A., Jamal, H., & Whittington, D. (1992). Willingness to pay for water in rural Punjab, Pakistan. UNDP-World Bank Water and Sanitation Program, World Bank.
Lua i Stíl Chicago (17ú heag.)Altaf, Anjum, Haroon Jamal, agus Dale Whittington. Willingness to Pay for Water in Rural Punjab, Pakistan. Washington, D.C: UNDP-World Bank Water and Sanitation Program, World Bank, 1992.
Lua MLA (9ú heag.)Altaf, Anjum, et al. Willingness to Pay for Water in Rural Punjab, Pakistan. UNDP-World Bank Water and Sanitation Program, World Bank, 1992.
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