Sudrajat, Sudradjat, et al. “Influence of Manure, Nitrogen, Phosphorus and Potassium Fertilizer Application on Growth of One-Year-Old Oil Palms on Marginal Soil in Jonggol, Bogor, Indonesia”. Journal of Tropical Crop Science, vol. 1, no. 2, Dec. 2014, pp. 18-24, doi:10.29244/jtcs.1.2.18-24.