Philippines (Republic) Bureau of Soil Conservation. Soil erosion. Office of Agricultural Information.
Chicago-referens (17:e uppl.)Philippines (Republic) Bureau of Soil Conservation. Soil Erosion. [Manila: Office of Agricultural Information.
MLA-referens (9:e uppl.)Philippines (Republic) Bureau of Soil Conservation. Soil Erosion. Office of Agricultural Information.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.