Nelson, Paul, Rhebergen, Tiemen, Berthelsen, Suzanne, Webb, Michael, Banabas, Murom, Oberthur, Thomas, Donough, Chris R., Rahmadsyah, ., Indrasuara, Kooseni, and Lubis, Ahmad (2011) Soil acidification under oil palm: rates and effects on yield. Better Crops with Plant Food, 95 (4). pp. 22-25.