Faustina, E., and S. Supijatno. “Optimization of Nitrogen and Phosphorus Fertilizer on Two Years Old of Oil Palm(<i>Elaeis Guineensis </I>Jacq.)”. Asian Journal of Applied Sciences, vol. 3, no. 3, June 2015, https://www.ajouronline.com/index.php/AJAS/article/view/2669.