“Zeolite Utilization As a Catalyst and Nutrient Adsorbent of an Organic Fertilizer Process From Palm Oil Mill Effluent As Raw Material”. JOURNAL OF TROPICAL SOILS, vol. 18, no. 3, Sept. 2014, pp. 177-84, https://doi.org/10.5400/jts.2013.v18i3.177-184.