Graaff, J. d. (1996). The price of soil erosion: An economic evaluation of soil conservation and watershed development. Wageningen Agricultural University.
Chicago-referens (17:e uppl.)Graaff, J. de. The Price of Soil Erosion: An Economic Evaluation of Soil Conservation and Watershed Development. Wageningen, Netherlands: Wageningen Agricultural University, 1996.
MLA-referens (8:e uppl.)Graaff, J. de. The Price of Soil Erosion: An Economic Evaluation of Soil Conservation and Watershed Development. Wageningen Agricultural University, 1996.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.