Sulakhudin, ., A. Syukur, and B. H. Sunarminto. “Zeolite and Hucalcia As Coating Material for Improving Quality of NPK Fertilizer in Costal Sandy Soil”. JOURNAL OF TROPICAL SOILS, vol. 16, no. 2, July 2013, pp. 99-106, doi:10.5400/jts.2011.v16i2.99-106.