Soil conservation and sustainable land use : an economic approach / Jan de GraaffThe price of soil erosion : an economic evaluation of soil conservation and watershed development / J. de GraaffThe price of soil erosion : an economic evaluation of soil conservation and watershed development / J. de GraaffThe price of soil erosion : an economic evaluation of soil conservation and watershed development / Jan de GraaffThe economics of coffee / J. de Graaff
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Differences between farmers and scientists in the perception of soil erosion : a South African case studey / Serge Cartier van Dissel, Jan de GraaffWater harvesting in Mediterranean zones: an impact assessment and economic evaluation : proceedings from EU Wahia project final seminar in Lanzarote / Jan de Graaff and Mohamed Ouessar (eds)